To chose the appropriate free-hub, there are two aspects to keep in mind.
First, you need to be able to mount the free hub on the hub. Not all free hubs can be interchanged with each other, so you won't be ale to replace it with any random free hub. In order to chose a correct free hub, you need to check if it's compatible with the Giant Alloy centerlock disc hub.
Second, you need to make sure that the free hub you select is a Shimano 10 (or 11) speed compatible one. As for example Campagnolo has a different layout of the "exterior" of the free hub, you won't be able to mount a Shimano 10 speed cassette on a Campagnolo compatible free hub.
Update: If you have a Gaint bike and the wheels are the stock version, you're likely to find the proper part number on www.giantbikespares.com.
Don't be afraid to use a Shimano 11 speed free hub. An 11 speed free hub would require a small spacer to compensate the slightly narrower 10 speed cassette but this works without any problem. In fact, Mavic shipped their wheels already with this kind of free hubs years before the 11 speed drive trains hit the market.