Hello Tania,
Hmvproj is the utility that allows you to move or copy all the data for a project from one Harvest database to another Harvest database. You mentioned "database copy files". Does this mean you have taken a backup or export of your Harvest 12.5 database?
The database you are moving your project from and the database you are moving your project to should be at the same schema level, however I just tried a very simple test and the move completed successfully, so you should be able to move projects directly from a Harvest 12.5 database to a V13 database.
Here is where you can read more about this command: hmvproj Command-Move or Copy Projects.
Let me know if you need more information.