How to put a file in a folder in C++?

I am writing a program in C++ that is supposed to store user informations inside of a file (The os is Windows 10).

Here is the function:

void new_user()
{
    std::string user_name, user_surname, user_username, user_password;
    std::cout << "Name: "; std::cin >> user_name;

    std::cout << "\nSurname: "; std::cin >> user_surname;

    std::cout << "\nUsername: "; std::cin >> user_username;

    std::ofstream FileInfo = create_file(user_username + ".txt");
    FileInfo.close();
}

And this is the create_file() function:

std::ofstream create_file(const std::string & Path)
{
    std::ofstream File(Path,  std::ios::out | std::ios::app | std::ios::binary);
    File.close();
    return File;
}

I am trying to store the file into a folder like that:

    std::ofstream FileInfo = create_file("/Users/ " + user_username + ".txt"); // here is what I have tried 

However, what I have tried does not work properly, in fact it does not create any file or folder.

What should be the solution?