How much dry ice do I need for a 26 quart cooler?

I'm going camping for 2.5 days and want to get dry ice to keep drinks and some food cold since we'll be in the desert. I would prefer to get a styrofoam cooler so I can throw it out after, but if I have to get a regular cooler, it would probably be around 26ish quarts. Im not sure how big the styrofoam cooler is. How much dry ice should I get and can I use a styrofoam cooler?