New player- why can’t i feed my animals?

hi i’m a new player on nintendo switch, only been playing a few days. i’m so confused. why are all my animals dying 😭 it’s saying they’re starving but im doing what i think is getting their food in the store room but it’s saying there’s no supplies?? i’m so confused on how to actually buy the food. i know this might sound dumb and idk if it’s a bug but it’s annoying me