I purchased an M4 iPad Pro and it arrived today. I went to set it up from my previous iPad Pro but it is running iPadOS 18, and 17.7 is the highest for the M4 currently. I updated on the 17th I think (a day or two after 18 came out) and wondering if I should wipe the new iPad and start again and try using a 17.x backup, or set up as a new device.
I ran into this a bit over a week ago when I upgraded. I had been running the public beta on my 2020 iPad Pro, and upgraded 2 days after 18 officially launched, but after it was pulled for bricking M4 Pros. It sounds like 18.0.1 is in progress and should be out soon, however I installed the 18.1 public beta on mine after seeing others have success with it from 17.7.
That said, my prior upgrade sat around for at least a week before I threw the beta in and there were no issues.
If you have another iOS device, you should be able to go to settings>Account Settings (the one with your Memoji)>iCloud Backup and see all backups stored in your iCloud.
I am only able to see the most recent back up. I thought I would be able to see them all as well. I could see a few while trying to set up the new ipad. But gave up and tried to update it to 18, before remembering it was pulled from m4s.