Ok super dumb question lol

I am beginning to type of my envelopes for my STD's...quick question about to how type it.

Mr. & Mrs. So & So
123 liwedding Dr.
Helpme, N.Y. 12345

lol- hope u like my address. Now I am stumped by the NY part do u put the 2 dots to seperate the letters or just leave it 'NY'