IMAC mid 2011 OS

What is the latest OS I can upgrade to on a mid 2011 IMAC? I currently am running sierra. I can see the big sur in the app store but get the message "This version of macOS 11.6 cannot be installed on this computer."

I don't see any of the others in the app store, Mojave, High Sierra, Catalina.

Thanks for any help!