So I passed the Jyly 2016 NY exam

Now I need to get my 50 pro bono hours.. I've exchanged a few e-mails with the pro bono manager of a large non-profit organization that offers legal assistance to the poor. The e-mails were somewhat informal in nature. She invited me to a meeting in anticipation of my joining the pro bono team.. So the million dollar question is what do I wear??
Do I wear the formal legal interview suit, a more casual business outfit - buttoned shirt & pants or a business casual dress..??
I don't want to overdress nor do I want to look disrespectful of the office - but I don't know anyone who has knowledge of the dress code in this office..
Thanks