How to gets contacts that weren’t originally backed up In iCloud

I backed my husband’s phone to iCloud because he upgraded from a 6 to an 8. When I did the restore a lot of his contacts were missing. I looked at his old phone in the backup section and his contacts were toggled off. Can I put his SIM card back in his old phone , toggle the contacts on, do a backup then move the SIM card to the new phone and do a restore and the contacts will appear? Or is there another way to do it so that I can get his contacts back? They are still in his old phone. Thanks