I have a macbook pro running Catalina 10.15.7 can I upgrade to OS 12 Sierra?

How to upgrade to macOS Monterey - Apple Support includes instructions for upgrading older Macs.

A Late 2013 MacBook Pro can be upgraded to macOS "Big Sur"; macOS "Catalina" for Early 2013 models.

Back up your data, check your applications for compatibility, and if your MacBook Pro is a late-2013 model, click on the download link for Big Sur in the Related Article above.

Sierra is 10.12, not 12, and would be a downgrade.

(224567)

10.12 Sierra is OLDER that 10.15 Catalina. If you are currently running 10.15 Catalina, you can not install an OLDER version of MacOS, unless you completely ERASE the drive (which discards all your files)

I think you mean to UPGRADE to MacOS 12 Monterey.

But if your Mac is early 2013 model it is not qualified to run MacOS 12 Monterey.

Umm ... let's clear up what you have and what you are trying to do ...

First thing to do is determine what MacBookPro model you have. Do what Grant Bennett-Alder suggested earlier to find out what model you have: Do  menu > about this mac and see what it says.

Then,

Catalina is macOS 10.15.x If you have a Mid 2012 or older MacBook Pro this is the latest version of macOS that you can install

Sierra was/is macOS 10.12.x Are you saying you want to downgrade your MacBook Pro from Catalina to Sierra?

Monterey is macOS 12.x MacBook Pro models older than "Early 2015 Retina" models cannot install Monterey

what model-year MacBook Pro?

 menu > about this mac

Hi,

Monterey is requirement Early 2015 or later, so you can't upgrade to Monterey, Catalina is the latest for your MacBook Pro.

eh? you're running Catalina and you want to run Sierra? It is not possible to downgrade macOS