C++ Threads Program

I am new to C++ and I am trying to get a threads to randomly move on a grid in any direction until its final destination is reached. I am not sure how to write that in the while loop of the walkerI function. I looked at many tutorials and read through c++ syntax but I am unsure on how to go about this. Maybe I am missing something very basic. Can I get some explanation on this/useful websites on how to do this. Thank you!

#include <iostream>
#include <mutex>
#include <thread>

#define N 1000
#define S 25
#define MAX_WALKERS_PER_LOCATION 3
#define MAX_WALKERS_PER_EDGE 4
std::thread thr[N];
std::mutex m; 

typedef struct Walker
{
    int currentX, currentY, finalX, finalY;
    bool hasArrived;
    void Init() 
    {
        currentX = rand() % S;
        currentY = rand() % S;
        finalX = rand() % S;
        finalY = rand() % S;
        hasArrived = false;
    }
} ;

int originalGridCount[S][S];  //used to make sure the number of walkers per location is within the limits.
int finalGridCount[S][S];  //used to set the result target.
int obtainedGridCount[S][S];  //something you may use for the results
Walker walkers[N];

void Lock(std::mutex* m)
{
    m->lock();
    std::this_thread::sleep_for(std::chrono::milliseconds(1)); //Sleeps to simulate longer execution time and increase the probability of an issue
}

void Unlock(std::mutex* m)
{
    m->unlock();
}

void PrintGrid(std::string message, int grid[S][S])
{
    std::cout << message;
    for (int i = 0; i < S; i++)
    {
        for (int j = 0; j < S; j++)
            std::cout << (grid[i][j]<10?"  " : " ") << grid[i][j]; //Initialising grids
        std::cout << "\n";
    }
}

void SetObtainedGrid()
{
    for (int i = 0; i < N; i++) //Initialising walkers' locations
    {
        obtainedGridCount[walkers[i].currentY][walkers[i].currentX]++;
        if (!walkers[i].hasArrived)
        {
            std::cout << "\nAt least one walker had not arrived!\n";
            return;
        }
    }
}

void CompareGrids(int a[S][S], int b[S][S])
{
    for (int i = 0; i < S; i++)
        for (int j = 0; j < S; j++)
            if (a[i][j] != b[i][j])
            {
                std::cout<<"\nError: results are different!\n";
                return;
            }
    std::cout << "\nSeems to be OK!\n";
}



void WalkerI(int id)
{
    while(finalGridCount != originalGridCount){
        
    }
}


void InitGame()
{
    for (int i = 0; i < S; i++)
        for (int j = 0; j < S; j++)
            originalGridCount[i][j] = finalGridCount[i][j] = obtainedGridCount[i][j] = 0; //Initialising grids
    for (int i = 0; i < N; i++) //Initialising walkers' locations
    {
        do walkers[i].Init();
        while (originalGridCount[walkers[i].currentY][walkers[i].currentX]>= MAX_WALKERS_PER_LOCATION);
        originalGridCount[walkers[i].currentY][walkers[i].currentX]++;
    }
    for (int i = 0; i < N; i++) //Initialising walkers' locations
        finalGridCount[walkers[i].finalY][walkers[i].finalX]++;
}

int main()
{
    InitGame();
    //Start your threads here.
    for (int i = 0; i < N; i++)
        thr[i] = std::thread(WalkerI, i);
    //Wait for completion of all threads
    for (int i=0; i < N; i++)
        thr[i].join();

    PrintGrid("Original locations:\n\n", originalGridCount);
    PrintGrid("\n\nIntended Result:\n\n", finalGridCount);
    SetObtainedGrid();
    PrintGrid("\n\nObtained Result:\n\n", obtainedGridCount);
    CompareGrids(finalGridCount, obtainedGridCount);
}