can i upgrade Imac pro mid 2014 with os 10.14.3 to os 10.15.x where can i find it to upgrade

There were no Mid 2014 iMac Pros. Are you referring to a Mid 2014 iMac or a Mid 2014 MacBook Pro? For those, Big Sur is the end of the line. You can upgrade from Mojave to Catalina, but I'm not sure what benefit there would be to stopping at Catalina.

If you are referring to an actual iMac Pro (2017), those can run Ventura, and will be able to run Sonoma when Apple releases Sonoma "this fall."

Back up your data, check the application compatibility table, click here, and then on the download link for it.

Catalina and above won't run 32-bit software; if you choose one of them, use Go64 as well.

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