That's a tough question to answer. The short answer is all of them. Because (almost) everything can be done with PowerShell, any questions are fair game on the exam.
The good news is you really don't need to memorize all of them. I would think about things that you are most likely to want to automate or write scripts for. Things like creating user accounts or adding printers. While there are a few cmdlets that deal with local policy, it's typically easier to use the Local Policy editor for that.
If I was going to make a short list of PowerShell cmdlets to be familiar with, it would include cmdlets that create or work with:
- Local Users
- Services, primarily how to list services, stop and start services
On the exam, Microsoft can ask about anything, but those are the more common cmdlets for this particular exam.