Shopping of food is pretty easy in Korea as everu locality has a grocery store or the MART as they Korean say. The famous big shoping stores are Lotte, Emart and Home-plus.
But the small locality stores are like Top-mart, GS mart, or Morning mart which are locally available in the city.
Another small convenience store are like Family part, Seven eleven etc which are little expensive then the normal marts but these marts are open almost 24hrs.
Also the Jangseon-po area has a new Mart called lotte Super instead of Morning Mart.
Also in Aju-dong a new Topmart Plus has be opened which is very near from Okpo.
So just enjoy shopping!!!!!!!!!