No problem to do it, but you'll need to order the dropouts AND axle from Giant.
The Giant dropouts have a proprietary thread pitch and only Giant axle will work (even though it's a DT Swiss made axle)
There's a chance that the 3 might be shipped with the dropouts. Ask your LBS what came in the box.
My 3 did not come with any dropouts. LBS quoted me $13 for the 142x12 dropouts, but couldn't find the axle in the system (so take that price with a grain of salt).
$13 sounds about right for the dropouts. Axle should be about $50
Not sure why it's not showing up in the system. Have your LBS ask their Giant rep for part #.
Another option that's worked well for me is to message Giant directly on Facebook. They usually respond to questions within a few hours.
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