can i upgrade my 2012 iMac to APFS format

Be aware, also, that if you upgrade to macOS Catalina, any 32-bit applications will no longer run on your iMac. Catalina supports only 64-bit apps.

You can check to see what apps will be affected by clicking Apple menu > About This Mac > System Report.

Then scroll down the list on the left to Software > Applications.

The result will be a list of apps and whether they are 32-bit or 64-bit apps. The 32-bit apps will not run under Catalina so you will need to find updates or replacements for them.

BDAqua wrote:

I hear that Catalina/10.15.x is pretty miserable experience on old Mac Pros.

The OP has a 2012 iMac, not a Mac Pro. FWIW, Catalina runs just swell on the 2012 iMac I still have.

You can upgrade to Catalina.

How to upgrade to macOS Catalina - Apple Support

What SW is it that you need?

I hear that Catalina/10.15.x is pretty miserable experience on old Mac Pros.

OOPS! :O

Yes oops. Probably distracted trying to think of something negative to say. 😝