After your hour for the range is up, do you have to pack up and go back up front to pay for another hour? Or can you pay for 2 or 3 hours when you first come in?

You can pay for 2 hours up front when you first arrive to prevent packing up and leaving after the first hour is up. Just let them know.

You can probably pay for more hours when you first walk in if they're not expecting to be busy. Otherwise I'm sure you can pay for another hour if you walk up to the counter when your initial hour is done