iPad and iPhone have two different Apple IDs
Trying to help my husband. He somehow ended up with a different Apple Id on his phone than what he has on his iPad (two different clouds). Thus they are not connected. His phone has a lot of videos and music that he doesn't want to lose (all on that Apple ID which is not his original/primary Apple ID that he would want to continue to use). The music on the phone is from Apple Music (which is also linked to that one Apple Id). What would be the best course of action to get both devices on only one Apple ID, so that the devices will be linked, but without losing anything from either of the devices?
iPhone SE