Which subway do you take from Radio City Music Hall to Penn Station?

Take the Uptown E train (of the A-C-E, the blue line), 3 stops, from 34th Street-Penn Station to 7th Avenue.

Transfer at 7th Avenue to the Downtown B or Dtrains (of the B-D-F-M, the orange line), 1 stop, to 47th-50th Street-Rockefeller Center.