How to extract files from the game?

Recently, out of boredom, I started playing the Castle Crashers game with a friend, well, I went to the play ground to see if there was something interesting, I stumbled upon a person who made a skin for this game, and I became very interested in how to extract the game files, let's say the same character, How to extract his modelku change it and paste it back? I would be very grateful if someone explains how to extract files)