Antonioseyers

I would definitely provide ALL the paperwork (*not a legal advice): the fact that your record was expunged doesn't mean that this record has never existed before. As far as I understand, Federal agencies like USCIS have access to complete criminal history of all applicants, including expunged records. Just be truthful: it will attest to your moral character. Besides, possession of less than 50gr of marihuana was not a big deal in NJ even back then (not like [some other country] where you can get almost 10 years for less than 7gr). So just provide everything and don't stress about it.  

I thank each and everyone of you for providing feedback. I will seek for a lawyer.  I also found this information from Uscis.
A simple minor offense of marijuana will not affect my case but then again we never know what can happened.so I will find a lawyer to handle this matter.
 
Exception for Single Offense of Simple Possession
The conditional bar to good moral character does not adhere “if the violation was for a single offense of simple possession of 30 grams or less of marijuana.” (Emphasis added.) The exception also applies to paraphernalia offenses provided that “the paraphernalia offense is 'related to' simple possession of 30 grams or less of marijuana.”

I am saying just to include the info as immigration wants to know everything about u /don't leave it out/ if its not important to the officer,   then no need to worry