I really hope someone can please chime in and help me out. I was trying transfer my photos from my old 2009 iMac to my new 2019 iMac. In the process, something went wrong and the pictures didn't transfer over. Now on my 2009 iMac, when I open Photos, I get the error message that my library is not supported and I need to upgrade. Only I can't upgrade as my I am running 10.13.6 High Sierra. Can someone please help and tell me what I need to do to get my pictures back? Thanks!