Hi Tracie. I'm Greg, an installation specialist, 10 year Windows MVP, and Volunteer Moderator here to help you.
How were these photos imported? Did you pay attention to where they were going? It's best to put them in the C:\User Pictures folder which is already linked to the Photos app so they'll display there too.
If they're not there then do any of them have names or tags you can search for?
If not then can you import them again and this time pay attention they go into the Pictures folder. If you run the import program you used it should tell you where they were put.
Let me know what you find. I will be here to help until this case is resolved.