compiling multiple files using templates in cpp [duplicate]

I am learning cpp and I am creating a Vector class using templates, namespaces, header files... . Now this is my code so far

main.cpp

#include "my_vector.h"
#include <string>
#include <iostream>

int main(){
    MY::Vector<int> vector;

}

my_vector.cpp

#include "my_vector.h"
#include <string>
#include <iostream>


// implementation of all the constructors

template <class T>
MY::Vector<T>::Vector(){
    size = 0;
    alloc = 20;
    ptr = new T[alloc];
}

template <class T>
std::ostream& operator <<(std::ostream& out, const MY::Vector<T> vector){
    for (auto iterator = vector.ptr; iterator < vector.size; iterator++){
        out << *iterator;
    }
    return out;
}

template <class T>
MY::Vector<T>::~Vector(){delete[] ptr; alloc = 0; size = 0;}

my_vector.h

#ifndef MY_VECTOR_H
#define MY_VECTOR_H

#include <string>
#include <iostream>

namespace MY{

    template <class T>
    class Vector{

    public:
        // these are going to be some friend functions
        // we are going to overload the operator << to print the content of the vector
        friend std::ostream& operator<<(std::ostream& out, const Vector<T>& vector);

    public:
        // we need to store three things
        // pointer to the first address in memory
        // size of the vector so far
        // actual space allocated
        T* ptr;
        size_t size;
        size_t alloc;

    public:
        // we need 2 constructors

        // default constructor
        Vector<T>();

        // custom constructor
        Vector<T>(T value);

        // overloaded custom constructor
        Vector<T>(int cells, T value);

        // destructor
        ~Vector<T>();

        // Now the copy constructor
        Vector<T>(const Vector<T>& other);

        // Now the move constructor
        Vector<T>(Vector<T>&& other);

        // now a copy assignment
        Vector<T>& operator=(const Vector<T>& other);

        // now a move assignment
        Vector<T>& operator=(Vector<T>&& other);

    public:
        // these are all the functions that we need
        bool isEmpty();
        size_t get_size();
        size_t get_alloc();
        void push_back(T value);
        void push_front(T value);
        void pop_back();
        void pop_front();

    public:
        // these are the overloaded operations
        // symbol > if one vector is greater than another one
        // opposite goes for < operator;
        // operator << to print the content of the vector using friend functions
        // operator + to add two vector together
        bool operator>(const Vector<T>& other);
        bool operator<(const Vector<T>& other);
        Vector<T>& operator+(const Vector& other);
    };
}
#endif

As you can see most of the stuff is just declared. However I already implemented the default constructor and the destructor to test if everything is fine so far, and it seems it is not as I am getting this error

Undefined symbols for architecture x86_64:
  "MY::Vector<int>::Vector()", referenced from:
      _main in main-08d713.o
  "MY::Vector<int>::~Vector()", referenced from:
      _main in main-08d713.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
run.sh: line 3: ./output: No such file or directory

additionally I am compiling using this a bash script like this

#!/bin/bash
g++  *.cpp -o output -std=c++17
./output

I have also tried simply

g++ *.cpp
./a.out

I cannot really understand where is the problem. Could someone help?