Photos App - Identify photos without referenced files

[ptrkllpry]

How do I determine which photos are missing reference file without having to individually click on every photo in my library (35k photos)

I am moving library to icloud and I am getting an error message that it cannot locate some referenced files. I go through process of trying to locate two files, then is gives a general error saying there are multiple missing referenced files and if I should continue to upload without them.

I want to be able to see what photos having missing originals so I can pull them from the backup or other external drives that they may be located.