Organizing Functions in Files in VS

I’m having some issues at the end of Organizing Functions in Files section of the C++ fundamentals course. No problems are showing in the console, but when I try to run the program I get this

undefined reference to `greet(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >)'

Here is the code in main.cpp

#include "util\greet.hpp"
using namespace std;

int main(){
    return 0;

here is the code in greet.cpp

using namespace std;

void greet(string name){
    cout << "Hello " << name;

and finally greet.hpp

#define UTIL_GREET

#include <string>

//Function declaration
void greet(std::string name);


I have checked and made sure the directory in the include statement is correct and even tried the full directory to no avail. I would really appreciate any and all help on this topic.

Send complete codes and hierarchy of your project.