There a different ways to import/ export data.
You can use:
So as you can see there are many modules available that are able to import/ export data in your application.
Hope this helps find the right solution.
EDIT: As Enzo mentioned, you can also import/ export data using Web services, REST services, more about that on the following page: https://docs.mendix.com/howto/integration/
EDIT 2: As Rob mentioned: Also don't forget the Database Replication Module! https://appstore.home.mendix.com/link/app/160/Mendix/Database-replication
EDIT 3: You can also import/ export data using backups https://docs.mendix.com/developerportal/operate/backups