you can reuse all the bolts and nuts you took off. Just put them to a wire brush or wire wheel to clean them up and put a dab of blue locktight on each of them on the threads. It helps to run a wire brush though the threaded parts if its really rusty or cruddy. If the bolts you took out are covered in rust on the threaded area it was seated, clean up both the threads and the bolts.
Even the axle nut on the rears is 100% reusable. please buy new cotter pins though, never reuse a cotter pin.
When you tighten up the axle nut, its finger tight then rest your hand and the weight of your arm from gravity only on the end of the wrench and spin the drum in reverse, lossen it up and repeat this step 2 times. put the castle nut on and the cotter pin in, your done.