Lori, it's a good sign that Photos is working on you iPad. I think we need some more information. How is your Lacie drive formatted? Is the package file "Photos Library.photoslibrary" on that drive? Is the package file "Photos Library.photoslibrary" in the Pictures folder on your Mac? If not, can you copy it back to your Mac? How much storage space is available on your Mac, and how big is the Photos Library? Does your iPad show all your pictures? Do you see all your pictures in Photos at iCloud.com?
What version of macOS are you running? What version of iPadOS are you using? How much storage space is available on your Mac, and how big is the Photos Library?
Anything else that might help?