AS an alternative to Sarah's method, just type molly maguire into the very useful "Digitrad and Forum Search" box on the main Forum page; it searches the Forum and the Digital Tradition database, and will get you not only the words you are looking for, but a number of discussions with related songs and background information.  A search for molly mcguire would get you fewer hits, but would show you the more usual spelling of the name in this context, which you could then use to expand your search.

Malcolm