Not recommended/don't do it--- why do you want to do this?
Hatcheries ship 25 or more together so they can keep each other warm, and they ship 1 day old chicks- as they can survive 2-3 days on the remaining yolk in their abdomens. This is still hard on them, and shipping losses often happen. They pack them in to a small but strong box with air holes and a pad for traction and a bit of insulation. Older birds can be shipped- like 3mo and up, they are old and large enough to keep themselves warm, and will eat apple slices packed with them to keep from dehydrating and dying. A week old chicks is a fragile thing, they need to stay warm and have access to chick food & water at all times. The boxes can get turned upside down, there is no way to send food and water with them, even if you got a battery pack heater to keep them warm. You need to wait until they are much older and can survive 2-3 days on apples or similar. If a person wants these, they need to pick up or you need to drop them off in person- or wait until they are much older to ship.