I use the Pro 12.9 - Roastmaster shines on the larger screen - full support.
Make sure your old iPad is being backed up by iCloud, and that Roastmaster is selected in Settings > iCloud (both are true by default). If so, then just choose to Set Up or Restore from iCloud Backup when you set up your new Pro. When done, your database will be in place on your new device.
Every once in a while, a restore will go wonky, so I also advise to export you current database and save to iCloud drive in case something goes wrong - just as a precaution. On the home screen, open the drum door and tap Utilities > Export Current Database. Save it to iCloud. If you ever need to restore it, just tap "Import to Roastmaster" from the backup file in the iCloud drive app - Roastmaster will import it, then just "activate" it from the database details screen to use it.