Where and how to get instrument files and use them? - MuseScore 2

Hello!

I'm working on a piece but it's default "piano" instrument sounds like plastic and robotic. I know what a Soundfont is, but I just need an authentic piano instrument and not change the whole interface. I have looked for MusicXML files but can't find any (especially piano) and when I go into the directory of the instruments they are not MusicXML files they are "Compressed MuseScore Files". Should I be looking for MusicXML or something else? Please help. Thank you in advance! :)