@Canice *****
should be good, most offices want the little white paper slip that says it's your first 90 day report (the one they usually put in your passport when you get your first long extension), a filled out TM47 application for 90 day report (which you can get at the office when you show up) and your passport.
Did they give you this paper when you got your extension (I mean is that how you know you need to do a 90 day report)