C:\Users\"Computer Name"\AppData\LocalLow\IronGate\Valheim\worlds
Is where my default save data folders are.

Inside the folder I have 2 different kinds of backups.
The older ones that are "worldname".db.old and "worldname".fwl.old
You would just delete the ".old" part for both files and it would be a previous backup save.

There is a "newer" interface inside the game where you can actually hit a drop down on the world and see the back ups and launch the game from said backup though. I don't know if it's the same for cloud storage, since it's highly recommended to NOT use cloud storage, as most of the save issues are from the cloud storage.