piracy

I pirated Deltarune because I was dirt broke and wanted to play the new chapters. I'm in a better position now, and would like to actually buy the game. Does anyone know where the saves would be stored? I want transfer and back them up, then load them into the Steam version. I played it on the Steam Deck then loaded it through Proton, and I'm not used to messing with Proton/Wine nonsense very much, so I don't know how the file stuff works.