Just to add to this, although it's something you can work out easily enough (as above) you'll probably find you just fly to whatever you're given. You wouldn't normally make a conversion.
For example, the airfield I fly from is at en elevation of around 200ft AMSL, circuit height is 1200ft AMSL. On the ATIS recording you get given the QNH, but the tower often give the QFE verbally. So you have the choice to set QNH and fly at 1200ft in the circuit, or set QFE and fly at 1000ft, as indicated on the altimeter. It makes no difference.
If you're only given one of them at any given airfield, you'd probably just work with that as opposed to converting.