i have a i mac mid 2011 can i update it beyond serria

You can update it to macOS 10.13 High Sierra, but that is as far as it can go.

It cannot run 10.14 Mojave, 10.15 Catalina or the current macOS 11 Big Sur.

See here to update it: link-> How to get old versions of macOS - Apple Support

The model year of an iMac is available at Apple menu > About This Mac.

A late-2009 through mid-2011 iMac can be upgraded to High Sierra 10.13.6 but no later version. See: https://support.apple.com/en-us/HT211683