Sorry if this is a dumb question, I've been searching but can't really find the answer. I know money orders need to be purchased with cash or debit. What I can't figure out is if you can buy a money order with an American Express Serve card at Walmart or anywhere else? "American Express" means credit card to most people, but it is in fact a prepaid debit card. Can this simply be swiped with a PIN and used as a debit card?