How do i know which wheels will fit my bike?
Unless the Oz version is different from the US version (which it doesn't seem to be; the picture is the same), it looks like this bike uses a by default regular old 135x5 mm quick release, so the wheel needs a quick release compatible hub (not a thru axle hub).

Have you tried servicing the existing wheel? QR skewers and new axles are way cheaper than a new wheel (but of course, thru axles are stronger, so the upgrade may be worth it anyway).

Edit: It looks like Giant has a conversion kit you can buy to go to 142 x 12 thru axles wheels. 

A picture of the kit is here:



Looks like the two pieces on the left screw into both places where the skewer passes through, then the hanger is replaced as well. You can see this video on how to install it. 

It also looks like you need a particular thru axle specifically from Giant due to threading; it looks like its a re-badged DT Swiss thru axle, so maybe they have something compatible.