how many marshmellows would you need to put in a pillowcase to make it like a real pillow?

we were thinking about proper new years resolutions for when it happens and my wife thought that maybe we could become vegans and recycle more like these 2 guys she saw on a tv show but she said if we do it then we need to be full-on and not like people who just do it for the fame or to make a point or whatever and part of that is we can't have any animal-prroducts at all like shoes even that have leather on them or milk cubes or regular pillows she said becuase they have feathers from malllards in them and something about upholstery. for the shoes we figured we can get around it by doing slippers and i never liked the milk cubes anyway but with the pillows the best alternatvie we could think of was filling the pillow with the jumbo marshmellows and as long as they're in a plastic bag and then wrapped in the pillow case it shouldnt matter how old they are or anytthing but we're not rich either and can't buy so many marshmellows so how many exactly do you think we sshould be planning on to do this resposnbile and not be even more broke than whats now.