How to download an icloud backup
I have an icloud backup from my 7 and now that I have already tried setting up my 12 mini I'm unsure how to access the backup to download on the 12 mini.
iPhone 12 mini, iOS 16
You don't need to go hunting for your backup, it will be found by your new device when you set it up.
See Apple's instructions Restore your device from an iCloud backup in Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Note Apple's comment If you already set up your device, you need to erase all of its content before you can use these steps to restore from your backup. This might apply if you have set up your iPhone 12 but did not choose to restore your backup from iCloud.