Hey! Sorry to hear that you're having trouble with it. The reason for the files being different is because 1.13+ worldedit uses .schem instead of .schematic (at least I think that's why).
I can convert it to a .schematic file if you want but there are going to be blocks missing since this uses blocks from versions 1.13 and 1.16. If you're okay with that then I can go ahead and convert it for you. If so, would you like the link sent to you on here or somewhere else? (discord, email, etc.).
Modern House #1 on August 30th, 2021 12:12 PM EST