I suspect that if the juvenile matter appeared on the background check, that it is instead a conviction that would prohibit you under both Maryland and federal law from possessing a firearm. Even if it were not a criminal conviction, Maryland and federal law prohibit certain people from possessing firearms under other circumstances that are listed in Md. Public Safety Code Ann. § 5-101, et. seq. and 18 U.S.C. section 922(g). Beware that the Maryland and federal statutes are similar, but they are not the same.
In order to give you a precise answer to your question, any lawyer would need the details of your prior case. However, I do not recommed that you post additional details about yourself, in this forum, because anyone, including law enforcement, might use it against you. Instead, read the statutes, and if you still have questions, seek a confidential consultation with a criminal defense lawyer.