How to transfer a function from main to a class method file?

I have a problem with my code. In main(automoto.cpp) I have created a function that I would like to transfer to the file vehicles.cpp

This is how it looks:

automoto.cpp

    #include "vehicles.h"
    #include <iostream>

    using namespace std;

    void add_vehicle(Vehicles**&, int&);

    void Loop(Vehicles**& v, int &size) { ////// is responsible for adding
        char e_add;// = 'N';
        do {
            add_vehicle(v, size); 
            v[size - 1]->add();
            cout << "Do you want to finish adding? Click Y/N: ";
            cin >> e_add;

        } while (e_add == 'N'|| e_add == 'n'); //while (p[size]->e_dod == "N" ||p[size]->e_dod == "n");
    }

    void print(Vehicles** vehicles, int size) {
        std::cout << "====================================" << std::endl;
        for (int i{ 0 }; i < size; i++)
            std::cout << "Type: " << vehicles[i]->get_type() << " Brand: " << vehicles[i]->get_brand() << " Model: " << vehicles[i]->get_model() << " Price: " << vehicles[i]->get_price() << std::endl;
    }


    void delete_v(Vehicles**& vehicles, int& size) {
        for (size_t i{ 0 }; i < size; i++)
            delete vehicles[i];
        delete[] vehicles;
        size = 0;
        vehicles = NULL;
    }

    void delete_v(Vehicles**& vehicles, int& size, int index) {
        if (index < size) {
            Vehicles** temp = new Vehicles * [size - 1];
            short int j{ -1 };
            for (size_t i{ 0 }; i < size; i++) {
                if (i != index) {
                    j++;
                    temp[j] = vehicles[i];
                }
            }
            delete[] vehicles;
            --size;
            vehicles = temp;
        }
        else
            std::cout << "Memory free!" << std::endl;


    }



    int main()
    {
        Vehicles** veh;
        int size{ 0 }, index{ 0 };
        Loop(veh, size);
        print(veh, size);
        delete_v(veh,size,0);
        print(veh, size);
        delete_v(veh,size);


        return 0;

    }

    void add_vehicle(Vehicles**& vehicle, int& size) {
        Vehicles** temp = new Vehicles * [size + 1];
        if (size == 0)
            temp[size] = new Vehicles;
        else {
            for (int i{ 0 }; i < size; i++)
                temp[i] = vehicle[i];
            delete[] vehicle;

            temp[size] = new Vehicles;
        }
        ++size;
        vehicle = temp;
    }

vehicles.cpp

#include "vehicles.h"

#include <iostream>

using namespace std;


void Vehicles::set_amount(int x) { amount = x; }

void Vehicles::add()
{
    cout << "ADDING VEHICLE..." << endl;
    cout << "Enter the vehicle type:";
    cin >> type;

    cout << "Enter the vehicle brand: ";
    cin >> brand;

    cout << "Enter the vehicle model: ";
    cin >> model;

    cout << "Enter the vehicle price: ";
    cin >> price;

}

vehicles.h

#include <iostream>
#include <cstdlib>
using namespace std;

class Vehicles
{
public:
    string type;
    string brand;
    string model;
    string e_add;
    int amount;
    int price;

    void add();
    int get_amount() { return amount; }
    string get_type() { return type; }
    string get_brand() { return brand; }
    string get_model() { return model; }
    int get_price() { return price; }
    void set_amount(int x);

};

Getting to the point - how can I transfer all the created main function to the vehicles.cpp file so that the program compiles? I would be grateful for the ready code, as tomorrow I have a deadline to submit the code, and the lecturer wants to have each of these functions in the class file.

EDIT

What exactly do I mean - these are my files, after moving the function:

automoto.cpp(main)

    #include <iostream>

    using namespace std;




    int main()
    {
        Vehicles** veh;
        int size{ 0 }, index{ 0 };
        Loop(veh, size);
        print(veh, size);
        delete_v(veh,size,0);
        print(veh, size);
        delete_v(veh,size);


        return 0;

    }

and my vehicles.cpp - where all the functions should be:

#include <iostream>

using namespace std;


void Vehicles::set_amount(int x) { amount = x; }

void Vehicles::add()
{
    cout << "ADDING VEHICLE..." << endl;
    cout << "Enter the vehicle type:";
    cin >> type;

    cout << "Enter the vehicle brand: ";
    cin >> brand;

    cout << "Enter the vehicle model: ";
    cin >> model;

    cout << "Enter the vehicle price: ";
    cin >> price;

}

void Loop(Vehicles**& v, int& size) { ////// is responsible for adding
    char e_add;// = 'N';
    do {
        add_vehicle(v, size);
        v[size - 1]->add();
        cout << "Do you want to finish adding? Click Y/N: ";
        cin >> e_add;

    } while (e_add == 'N' || e_add == 'n'); //while (p[size]->e_dod == "N" ||p[size]->e_dod == "n");
}

void print(Vehicles** vehicles, int size) {
    std::cout << "====================================" << std::endl;
    for (int i{ 0 }; i < size; i++)
        std::cout << "Type: " << vehicles[i]->get_type() << " Brand: " << vehicles[i]->get_brand() << " Model: " << vehicles[i]->get_model() << " Price: " << vehicles[i]->get_price() << std::endl;
}


void delete_v(Vehicles**& vehicles, int& size) {
    for (size_t i{ 0 }; i < size; i++)
        delete vehicles[i];
    delete[] vehicles;
    size = 0;
    vehicles = NULL;
}

void delete_v(Vehicles**& vehicles, int& size, int index) {
    if (index < size) {
        Vehicles** temp = new Vehicles * [size - 1];
        short int j{ -1 };
        for (size_t i{ 0 }; i < size; i++) {
            if (i != index) {
                j++;
                temp[j] = vehicles[i];
            }
        }
        delete[] vehicles;
        --size;
        vehicles = temp;
    }
    else
        std::cout << "Memory free!" << std::endl;


}

void add_vehicle(Vehicles**& vehicle, int& size) {
    Vehicles** temp = new Vehicles * [size + 1];
    if (size == 0)
        temp[size] = new Vehicles;
    else {
        for (int i{ 0 }; i < size; i++)
            temp[i] = vehicle[i];
        delete[] vehicle;

        temp[size] = new Vehicles;
    }
    ++size;
    vehicle = temp;
}

As you can see, I am trying to call the specified function in main (automoto.cpp), but I get the error "identifier not found", error C3861 in Visual Studio