Thanks for the question. One great resource I would recommend is a site called VolunteerMatch: https://www.volunteermatch.org
I did a search just using "STEM" as the search word for opportunities in the Trenton, NJ (I'm assuming it's New Jersey) area and here are some of the results:
Aquatic Sciences Education Program Volunteer at the Center for Aquatic Sciences at Adventure Aquarium in Camden: https://www.volunteermatch.org/search/opp2543504.jsp
Math & Science Tutor for the Philadelphia Education Fund: https://www.volunteermatch.org/search/opp2412322.jsp
There may be many other opportunities available that you can find using different search terms. It would also be a good idea to reach out to schools, public colleges, and other places where STEM opportunities may exist (even if they aren't overtly advertised)... you'd be surprised how many of them are looking for volunteers.