Yeah, unfortunately, your tray and save files are stored on your individual computer. You can use a USB drive, the cloud service of your choice, etc., to copy your old saves and tray files onto your new computer.
Yeah, I tried copying it over but they're still not popping up in my game. No saves or mods. There's not even a folder for them.
What method did you use to try to copy over your old files to your new computer?
When you start the game for the first time the Sims 4 folder with subfolders is created. Your old saves go in the newly created saves folder. Same with tray.
