Missing an Extensions File

Im trying to add a marching snare to musescore because musescore is too lazy to do it themselves. I was watching a video on how to do it and got to a part where they said go to the Extensions file in the Musescore 4 file. So I went there and there is no extensions there. What do I do. I want a marching snare. But I can't freaking download it. I am really starting to hate musescore the more I use it.