The upgrade to NetPhotoGraphics is pretty simple. The setup program will do all the database migration needed. But you should back up your database before upgrading because the zenphoto classic is not so good at database migration. Simply download the current single file release package from the GitHub repository: https://github.com/ZenPhoto20/netPhotoGraphics/releases
Use the setup-1.9.5.zip download as it is the most current with bug fixes.