thank you I appreciate your tolerance of us less learned in this area
To be precise, an 18-b is the "backup" assigned counsel for when Legal Aid doesn't/can't take the case. There is generally one or two assigned to the intake part of each court who pick up the extra cases. I'm not sure if they maintain a separate office (they are usually independent lawyers who are approved by the 18b panel to work), but you may be able to call the court with your appearance date to try to speak to one ahead of time.
Legal Aid does have their own office (usually in the courthouse), so if all else fails, call them.