icloud

I just bought a new iPad for my father. i had to create a new apple id for him, because he was having issues. so here is my problem. when i sign on with his new apple id - his photos from the old apple id - which were stored in iCloud - are not on his new ipad. if i log out and in with the old apple id- then the pics are there. how do i transfer or get the photos from the olde apple id, to the new apple id???