When you're compressing a new game that hasn't be investigated before, what you first need to do is find out what game engine said game is using.
You do this by using
steamdb or by looking at the game structure, if it follows [CodeName]\Content\Paks then it is unreal engine, if there's cas files, then it is frostbite and so forth.
You do this first step because such games already have plugins that can work with those games and can be found
here.
If it's a sequel to an already existing game, like Forza Horizon 5 and you're repacking Forza Horizon 6, then it is likely that the 6th iteration of the game uses the same method as the older game in which case, you should visit this
thread to see what methods were used for that older game(s).