Why can't I import all of my photos from my iPhone 5S to my Windows 10 PC?

I have 1,516 photos that I desperately need to removed from my iPhone 5S and imported onto my Windows 10 computer, but I'm running into a strange issue. When I go to the photos app on my PC, and click "Import from a USB device," instead of giving me the option to import and delete all 1,516 photos from my phone, I only get the selection to import 9 random pictures. And when I try to import the 9 random photos, it gives me an error. Please help?