Q: redeem content code in mac app store

Support provided content codes to update Pages, Keynote, and Numbers; the instructions provided Redeem iTunes Gift Cards and codes - Apple Support (are for iTunes) however if I follow these instructions using iTunes I receive an error message stating the code must be redeemed in the Mac App store - I haven't had any successful finding a support article.  Does anyone know how to redeem a code in the Mac App store?