That is a 12V DC flood light. you cannot just hook it up to a plug. you need to hook it up to a power supply. You overpaid too. return it if u can and get an AC model.
As for the 30" depth, let me get out my camera and show you a 30watt over my 125, 25" ish depth. I have no meter though so it will just be to show how bright the thing is.
I was wondering as I asked a similar question earlier, can't a DC light be wired to an 12v DC adapter? They're like 5$ on [Ebay Link Removed] I've had to wire a few dc connections in the past and this is what I did then.