You can see the app version from the Help > About page within the app.
App versions with a number like 6.3.11 exported databases as a text file with a .db extension and app versions with a date like 2022-05-20 export databases as a binary file with an .sqlite extension. If you are still using an app version from before May 2022, the easiest solution is to update the app, then export your database again.