iMac (27-inch, Mid 2011) running High Sierra version 10.13.6

Hello,

I have a Mid 2011 iMac running High Sierra version 10.13.6 and would like to upgrade to an OS version 10.14 or higher. I predominantly use my iMac to run Adobe Creative Cloud applications (Illustrator, Photoshop and Indesign) and am now being met with an incompatibility message when I try to update to the latest versions of the Adobe software.

The latest Mac OS is Catalina 10.15.7 which is not compatible with my iMac. Does anyone have any ideas how/if I can update to something higher than my current 10.13.6?

Thanks in advance

Gary