Cessna 172 pilot reported an NMAC event with a flight of three non-communicating aircraft. Upon establishing visual contact with the formation; the Cessna pilot executed a successful evasive maneuver.

Narrative

While operating VFR on an eastbound heading; I encountered a flight of [3] aircraft proceeding in loose formation in a northeast direction. At the time; I was communicating on the CTAF of the local airport while transiting their airspace.I attempted to raise the aircraft on the CTAF frequency as I saw their positions on ADS-B but only had one of the aircraft visually. I was reluctant to turn north because of aircraft operating at a nearby airport; and was reluctant to turn south as I did not have visual confirmation of the position of all three aircraft in the 'formation.'Because of the overcast layer above; my ability to climb was restricted by the ceiling.As I approached the formation flight; when I was very close; I finally observed all three aircraft and was able to execute a turn to pass over their path.I should have made a turn well before I approached them to eliminate the conflict well ahead of time; including a turn back to the west to create greater separation by flying behind their 'formation.' I was focused on visually identifying all three aircraft and my inability to contact them on CTAF; where an earlier decision to execute a turn around the other aircraft would have avoided this situation entirely.