Why wont icloud let me look at all of my backup storage?

My icloud says its almost full but it wont let me look at all of my storage. I have had 4 devices and I backed up all of my photos to my icloud. Now it wont let me download tem all to my pc. It only shows what's on my new device. How do I see all of my back up. Pease help me! I have racked my brain with this and I cant figure it out.