Please don’t judge me I’m young

So to get a money order, I need to get the cash from an ATM and then take it to a place like Walmart or a post office? Can someone explain to me how to get a money order? I’m really confused, nobody has taught me this . Will going to Walmart with cash for a money order work? What are other places that work? Need help understanding edit: the place I’m going to needs the order by 8 am but my bank doesn’t open until 10 am and it’s been closed all weekend so I need to go to an atm