I have a iPhone 12 mini

Make sure t is up to date on its iOS version. There are different ways to ensure the highest iOS that your device will support is installed on your device.

Any equipment currently running iOS 12.5.7 can't be updated to anything higher.

An iPhone 5S, 6, or 6plus, will only update to iOS 12.5.7

An iPhone 6S through 7, or SE(gen. 1), will currently update to iOS 15.7.5

An iPhone 8 or later will directly update to the latest iOS, 16.4.1

This support article has instructions about updating an iPhone or iPad wirelessly --> Update your iPhone or iPad - Apple Support

You can also use Mac and PC computers to update system software --> Update iOS on iPhone - Apple Support

When updating, your device will update to the highest version currently available that it will support, or it will just say it is up to date (and can't go any higher) and won't install anything.