If you are able to mail them via medial mail, like I am, if I don't have any, I get small shipping boxes from Walmart that perfectly holds at least that many for under 50 cents each. I bag them up in the bags I shared about earlier, with carboard on each side if not already boarded, and use either bubble wrap, packing peanuts, or as I have started using is the shredded up paper from my paper shredder for cushion. Make sure that all flaps on box are taped good, the label is taped on good, and you can print a label from going to Paypal, if they paid that way, and print off a label from their payment.
Make sure that they comics are well packed and box is well tapped as the USPS plays hockey with your packages.