Binary Converter

I am improving the files of a game that ended his activities in 2012 and I would like someone with knowledge in C ++, C and C # who could help me.

Basic explanation: The game files are made up of xmls that are converted using a compiler and become binary files, what I want to do is the reverse process: transform .b (binary) files into xml. Each version has a different compiler, I have saved compilers from previous versions for mold (I just don't have the source). I can send these compilers to you and also xml files for testing if you want to.

I can also send a video where a developer who created a functional binary converter explains how the program works and shows the source code.