Except we should go and buy food (ei mēti poreuthentes hēmeis agorasōmen brōmata). This is a condition of the third class with the aorist subjunctive (agorasōmen), where the conjunction is usually ean (with negative ean mē), but not always or necessarily so especially in the Koiné. So in 1Co 14:5 ei mē diermēneuēi and in Phi 3:12 ei kai katalabō. “Unless” is better here than “except.”
Food (brōmata), means eaten pieces from bibrōskō, to eat, somewhat like our “edibles” or vernacular “eats.”