String utf 16 to utf 8

Question

I am making a private dll hack for a game.
I am making things like chat commands now, and for that, I need to use strings with calling functions and checking for things. But the game is C# game and my dll is C++. And there is a difference between the strings. I saw someone who also made a dll for the game use
std::string NameOfPlayer = string_Utf16ToUtf8((name).c_str)
The .c_str I have and can use, but I also need the string_Utf16ToUtf8. Does anyone know what I need for that? I don't know how to make/use it because it doesn't exist.