ASRS 1987138

I was operating a piston helicopter (solo) from ZZZ1 traveling toward ZZ2, transitioning through ZZZ Class D airspace. This is a common VFR route that is used by many GA aircraft. The route from ZZZ1 to ZZZ is along [a highway], which is a bridge and causeway, running parallel with ZZZ3 Class B airspace. Before entering ZZZ class D airspace, I contacted ZZZ ATC about my intentions to transition through their airspace on the way toward ZZZ2. I was instructed to fly over the field at or above 1000 ft. At the typical point (toll plaza) I turned toward the Control Tower to fly over the center of the field. As usual, I ask for an altitude check and was told they saw me at 1000 ft. As I approached the airport, the ADS-B was starting to warn of "TRAFFIC 10 O'CLOCK". Just then, ATC sent a radio message "TURN RIGHT, TURN RIGHT", which I did. It was at that point I saw the aircraft at 10:00, approximately 200 ft. away fly past at 50 ft. below in a climb. If my position was one second later we would have intersected. As I was taking in what just happened, the ADS-B began to warn of other traffic, so I resumed my original course toward the tower. It appeared the ATC was very busy. I initially thought of yelling "[what] just happened?" but I just wanted to get clear of the airspace.