Pilot flying PA32 aircraft reported NMAC with another aircraft on final approach.

Narrative

In VMC conditions; Tower had instructed me to enter a right downwind [Runway] XXR and cleared me for XXR in the downwind. I entered a base turn for XXR; missed XXR (XXR is offset about 400 ft. to the south/southwest) and turned final for XXL. Another plane had been assigned XXL. Tower asked me what I was doing and I immediately went around. There several factors at play that; I believe; affected missing the assigned Runway.An unfamiliar Airport; seeing XXL and assuming that was the correct runway; and simply not being mentally set for the turn to XXR (the offset runway).Most of my training and flying has been at uncontrolled single runway airports. So; when I turned base; I saw XXL; very prominent; and my single runway experience kicked in. I didn't rehearse in my mind the base turn and that I needed to be looking for the offset Runway XXR. I believe that if I had visualized and rehearsed in my mind the pattern; I would not have missed XXR. I realize I could have been assigned a different runway; but I do think the principle is the same. It only takes a moment to reset if I already have the picture of the airport in my mind. So; the short of it; preparation; planning; implementation and mental focus were lacking in this case. Rehearsing for the flight could have been done at home at my desk or couch before ever departing.Also; I think; too much dependency on electronic flight bag may have taken away good old fashioned mental homework. The thinking being: 'How can I go wrong with all of these electronic aids'. Yes; I forgot to mention; my instrumentation was just upgraded from primarily analog to digital.