@Baja, there are three different ways to ask people, depending on your relationship/age of the Korean person.
In English, you'll say 'Where is ~ _____?' In Korean, you'll say '____ ~어디에요?'
If s/he's substantially older than you, use
____ 어디습니까?
If they're around your age, use
____ 어디에요?
If they're younger, use
____ 어디야?
Let's say it's Emart. Play it safe, and say this:
Emart 어디에요?
Adding -요 after the verb makes your sentence more polite, so you won't piss off any older Koreans.