Core Data model files don't use version numbers. The files might include a number in their name, but that's for people to see, Core Data doesn't care about it. It uses entity hashes to compare models.
The "main file" is the .xcdatamodeld
that contains all the versions (which have names ending in .xcdatamodel
).
Select that then look in the file inspector pane on the right. It has a pop-up menu that you use to select the current version.