Milika III

From Memory Alpha, the free Star Trek reference

Milika III is an inhabited planet.

Early in his career, Jean-Luc Picard led an away team on this planet to save an ambassador. This incident was mentioned by Q as one of the crucial events forming Picard's personality. (TNG: "Tapestry")

Judging from Q's speech, this probably took place before 2333, when Picard became captain of the USS Stargazer.