how do I get Mac OS 10.14 or later?

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.

A late 2012 through late-2013 iMac can be upgraded to Catalina 10.15.7. See: https://support.apple.com/en-us/HT211683

A mid 2014 or later can be upgraded to the current version of Big Sur. See: https://support.apple.com/en-us/HT201475

A late 2015 or later can be upgraded to the current version of Monterey.

Back up your data, check your applications for compatibility, and if your iMac model is recent enough, click on Mojave, Catalina, or Big Sur.

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