Giant ATX 2 2017 axle size? I have a Giant ATX 2 27.5 2017 and I broke my rear axle .

I sent it to my LBS, a week later they told me their axle fitted the front wheel but the back wheel was a different size.

They haven’t got the axle for it but at the mean time how do I get the axle size and what’s it most likely to be?

It has joytech hubs 32 spokes and has 27.5” wheels.
The info I have gathered on line suggests your bike is equipped with a 3x7 speed drive train. If that is the case the most likely axle is a 9mmx135mm QR (quick-release). You have apparently discovered the weak link in 7 speed freewheel drivelines. The issue with using a freewheel set-up is the drive side axle bearing is about 1.5 inches inboard from the edge of the frame. Unless you modify your riding style the axle is likely to break again. You can try to locate  a used 27.5 wheel with  an 8 speed cassette. Cassette wheels use a freehub not a freewheel. Freehub wheels mount both the bearings at the ends of the axle. You can have the rear derailleur adjusted to use only 7 of the rear gears. This will save the expense of buying an 8 speed shifter.