Photos not importing(some but not all)??

so this will be a long question. have a mid 2015 Mac air. only a 128ish HD. for some time now my wife has used a external HD for all photos by moving photo library to external drive. few days ago computer wouldn't power up. motherboard fried!! so new Mac air!! plug and play right??? NOPE. Set up new computer and then plug in external. emails and most files on new computer now. Photo library from external now on desk top. I wanted to just drag photos to new Photos App but noooo. So here is problem. did 2 things. copied the old photo library onto desk top and copied all 6,000 photos. all good!! the other problem is that when ever I open Photos App, it wants to open the old one. so I created a new photos's library. I tried to copy and drag and select all and import. I have 2,384 photos in my new library, but that is out of 6,197!! I get a window message that says "This item cannot be added to your Photo library because it may be an unrecognizable file format or the file may not contain valid data." File name

So, 6,197-2,384=3,813 photos that have this error.

Anyone have a solution for this error? Work around? I can not tell you if these 3k photos are in the cloud or not but they were in the old library.