Can my iMac use Big Sur?

I have a 27-inch iMac from late 2012. I need to update my Garagband app to the latest version, but it says I need an iOS that is Big Sur. But, I am running Catalina, and it looks like Big Sur does not run on my iMac 2012. What can I do to either get Big Sur or find a way to get the new Garageband on Catalina?