The number will be on a plate attached to the bar that goes behind the passenger and the drivers seats. It's slap bang in the middle so all you need to do is sit in either seat and turn around
Welcome to the forum, glad to see another anniversary edition joining the fold
EDIT: Also, you can put your number in this thread and hopefully get it added to the list.
http://www.350z-uk.com/topic/39625-370z-black-editions-whats-your-number/