How far back do iCloud backups go?

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.