Copied my imported photos from my old hdd. How do I import only my new photos?

[iMore Question]

I have an iPhone 4 and my old OS was Windows 7. I imported over 1700 photos and videos on my old hdd. I copied it to my new laptop running Windows 10. I copied it to the /Photos/Iphone/ folder (there are multiple imported folders under it) & edited the iphone import settings to make the that as the default folder. However now it finds all of the 2000 photos as new and asks me to import. I only want to import the new 300 odd photos. This is important, because my backup drive is configured with the folders and it will mess that up.

Thanks!