Depends on what device you're playing on!:
- If you're playing on Windows, Mac, or Linux, there's no need to do anything. Save files will transfer automatically!
- If you're playing on android, don't uninstall the game. Just install the new version over top of the existing one. Uninstalling the game will delete your save files.
- If you're playing on browser, don't play in incognito, and don't clear your cache. Or else your save files will be erased when you close it! As well, some browsers have security settings that prevent the game from saving. Chrome for example doesn't work for some, but Firefox does.