It is labeled "B" in your photo above. It should pull right off the studs.

The studs are a press fit in the hub, and I'm not sure if there is enough clearance to take them out without removing the hub from the spindle. If there is enough room, you can push them out by using a big C-clamp and a socket big enough to cover the head of the stud behind the hub. Put the socket over the head, hook the end of the C-clamp over the socket and push the stud out with the "foot" of the C-clamp.

I sense that you haven't done this before, and it might be a good idea to enlist the aid of someone who has been here before when you do this!

George