IPad restore from older ipad backup

I have a very old ipad running 12.4 and have backup it up on my mac. I am trying to restore it to an iPad Air which I have wiped and is running 13.3.3 with this data so my Dad can have a better iPad. But it tells me I cant as the ipad I'm moving the data to needs to be running the latest iOS. So I went to update it but it was already running the latest iOS it is able to run (13.3.3). So i tried an iCloud backup and that won't work either. Im stuck basically.

Any help appreciated

Nig