Acts 16:30

and brought them out There could be no fear that they would flee now who had remained when the open doors made flight easy.

and said. Sirs The Greek word Κύριοι implies an acknowledgment of great superiority. Those who had been his prisoners are now his "Lords."

what must I do to be saved? He had probably heard about the testimony of the possessed damsel, that Paul and Silas shewed the way of salvation, and now without knowing what it fully meant, he cries out (in his misery, when despair had prompted suicide) asking for the teaching which they had to give.