Export grayed out, photos missing

I was going to export a few photos I had taken in previous months and the "export" buttons are grayed out.  Then when I tried to do anything with the photos it said they are missing.  So I had it "find" the missing photos and it says the original can't be found.  This is happening with over 6,000 of my 7,500 photos and is a disaster.

Any help would be greatly appreciated.

Thank you,

Dave