Do not delete the old database. Do an export of the Photopost and then import it into the Vb
Since you have not deleted the old database yet Photopost still works.
Sign in and go to admin edit config
Change the database settings for photopost database to that as the same as your Vb
Then go to your Photopost and see that everything is running as it should.
Then simply delete the Photopost database. You should be good to go.