Update OS X El Capitan (Version: 10.11.6) to at least OS X Monterey (Version: 12)

Hi,

I've recently come into the possession of a used 2011 MacBook Air running on 10.11.6. I would like to use the latest version of Xcode on this device, but it requires OS X 12 or more.

There was one software update available and I downloaded + installed that, but the software version did not become 12 or more. I checked for more software updates, but none were available.

How can I update from 10.11.6 to 12+?

Thanks in advance.