Thank you for the information
You will need to apply for a Governor's pardon. You do that by contacting the Maryland Parole Commission (even though you were never on Parole) and request the Pardon application be mailed out to you. The MPC is the first step as they have the autonomy to review the file and then make a recommendation to the Governor. Of course, the Governor's word is definitive.
Now, I suggest that this is not an over night process. Getting a pardon takes time. There is a waiting list and once you name comes up an investigation is conducted as to your current life and character by interviewing your neighbors, family, friends, employers
I suggest that with the very negative tone here in Maryland toward the ownership of firearms you want to be sure not to make that your main focus of wanting the pardon and expungement. And the Governor has the right to give a partial pardon which would not restore your firearm rights.
Once you get a pardon, then you must Petition the Court of conviction for the expungement. The Pardon will not guarantee the expungement as that is entirely up to the court - but you are not eligible to petition the court without the expungement
Now, here is the contact of the MPC to call for the application and they can verify what I have just stated
Maryland Parole Commission
XXXXX Suite 307
And you can use this link to read more
Please note that I can only answer what you ask and so if you have more questions or need clarification, please ask it here. Otherwise, I thank you in advance for a positive rating.