Inside the "game" subdirectory you'll find a directory for "saves". You can grab that to manually back up your progress or transfer it to a new instance.
It may also be stored in your user's central configuration area, in which case your progress should persist between updates automatically.
Where this is all found naturally depends on your OS, so just search for "renpy saved data location". It's also good to know if you need to wipe everything and start over from scratch, something I had to do for another game recently.