all photos won't sync to my iPad Pro

I bought a new iPad Pro and restored it from the iCloud back up of my iPad2. The Pro is running 9.3.1. I have done an iTune sync using cable with my iMac twice. I choose "Sync all photos" and that screen shows 13,000+ photos. As the sync starts the screen says syncing 6,746 photos. It doesn't sync any photos prior to 2011. Checking the iPad after the sync confirms only 6.746 photos synced. I have 79.7G of unused space on the Pro. How can I get all of my photos onto the Ipad Pro?

Thanks in advance.