my mac pro is 2012 how do I upgrade?

macOS 10.15 Catalina is the end of the line for that MacBook Pro.

Check that your apps are all 64-bit using the Go64 tool, and upgrade or replace or retire any existing 32-bit apps.

If you are using Microsoft Office 2011 or earlier, this includes replacing the older Office with Office 2021 or an Office 365 subscription, or with one of various alternatives.

Ensure that all connected printer and scanner devices have Catalina driver versions available.

Get a complete and current backup prior to the upgrade.

Upgrade to Catalina.

How to get old versions of macOS - Apple Support

Back up your data, check your applications for compatibility, and click on Mojave or Catalina.

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