English countries put the month before the date in a sequence like that, so it would actually be "03/07/2013", "3/7/2013", or "03/07/13". The statement "It's the seventh of March" is perfectly grammatically accurate. You could also say "It's March seventh", though. However, TODAY is the nineteenth of March. I don't know if you're simply supposed to translate a sentence they gave you on a test or if you're actually trying to state what day TODAY is. If it's the latter, then the answer is "03/19/2013" or "It's March seventeenth" or some variation thereof.

We normally say: It's the seventh of March 2013. We normally write: It's 7 March 2013.