Trouble moving photos from Photo app to backup drive.

I imported a lot of photos (2-3 thousand) from my iPhone to my Mac a long time ago, and this resulted in many different photos sharing the same file name in my Photos library on my Mac. I want to transfer all my photos over to a backup drive but after several tries, I noticed that my Mac refuses to transfer photos with duplicate file names.(eg. both IMG_0991's cannot be moved out of the Photo app, due to them sharing their file name with another photo) Is there a way to solve this, my laptop storage is full and I really need the space taken up by my pictures.