You don't have to. If you use the newer .apk file to update the game then the saves aren't touched and you can continue your progress in the newer version without a problem.
If you get the newer version in a different way, you can load into any of your old game saves and select the in-game option to import/export save files to create a file of any save slot you want to transfer, and then use the same option in the menu to import it in the new game version.