With Purchase Orders PRO, ATUM locations have extra fields. To go to ATUM Locations go to the left WordPress panel > Products > ATUM Locations.
Get into a location that has been already created and you will see all these fields. Address, City, State, Postal Code, and Country are the new fields that belong to Purchase Orders PRO.
If you fill in all this information, and you set it to a Purchase Order in this location, the data will be automatically added to the Purchase Order. Check the screenshots below:
However, note that you can change this information manually in the Purchase Order.