My Photo Stream

My Photo Stream on my iPad has over 900 photos - mostly from a iPhone 4s that is no longer used but I do still have. I now have both an iPhone 5 and 5s as well as the iPad. Both the iPhones only have a little over 100 photos in My Photo Stream. When I put iCloud on my computer and uploaded the photos it only uploaded the photos from the Photo Steams on the phones. How can I get all the other photos to sync with all my devices? I thought if the photos were in My Photo Stream on any device they would be accessible from all my devices. Any assistance is appreciated. Thanks.