i need help with coding and where the code goes .h, .cpp, test.cpp and main.cpp

TION 2 Implementation Write an int value return function named binary_to_decimal that accepts a string parameter. The function will convert an 8 character length string from binary to decimal and returns the decimal. Do not use the C++ built-in functionality for this assignment, write the code from scratch. Testing Main Program Using loops prompt the user for a binary string value, validate the string for length 8 , the string must contain only 1 and 0 s (use the string contains function to make this easier). The program will run until the user opts out (types a character to exit the program)