Unfortunately Engine Prime does not read legacy drives. The export button at the bottom of Engine prime will overwrite the original database, so you should not do this if you want to keep your old drive.
The best thing to do would be to create a new drive for Engine prime and build your collection again.
Having said that, you can use the Engine 1.5.2 version and maintain legacy compatibility, or start fresh with the new Prime version and use the export button.
I hope this makes sense but if you have any questions please do not hesitate to ask