Upgrading 2012 iMac mountain lion
I have an iMac running mountain lion and would like a more recent os
Question marked as
A late 2012 iMac can be upgraded to macOS Catalina or earlier. See the following from Identify your iMac model - Apple Support
iMac (27-inch, Late 2012)
Model Identifier: iMac13,2
Part Number: MD095xx/A, MD096xx/A
Newest compatible operating system: macOS Catalina
iMac (21.5-inch, Late 2012)
Model Identifier: iMac13,1
Part Number: MD093xx/A, MD094xx/A
Newest compatible operating system: macOS Catalina
You will need to upgrade to El Capitan 10.11 as the first step. See information in macOS - How to Upgrade - Apple (SI)
Also see: How to download and install macOS - Apple Support
Be aware that if you upgrade to Catalina 10.15 or later you will also need to update any non-Apple 32-bit apps. See: https://www.stclairsoft.com/Go64/
or
https://www.macworld.com/article/232735/how-to-check-if-mac-software-is-32-or-64-bit.html