.celt files, I'm new and I need to convert one to mp3 Options

[YouGoByeBye]

I'm new at this whole thing, but I want to convert a .celt file into an MP3. The whole reason for doing this is because of a game I am playing. It has sound files that are stored inside of an .fsb file (This part doesn't matter to much because I already got them separated). In that .fsb file there are .celt files and from what I understand those are the actual sounds from the game. I need a simple way to convert those to a .mp3. Now I've read another post on here that says that they are now under Opus... I have no idea what that means, I searched it and came up with some .exe files that I have no idea how to use. So if some one can please give me a tutorial on how to convert a .celt file to a .mp3 file in simple English that would be amazing.