Name the number for margin of victory being 3 strokes
CREATE TABLE "alpg_tour_6" (
  "no" real,
  "date" text,
  "tournament" text,
  "winning_score" text,
  "to_par" text,
  "margin_of_victory" text,
  "runner_s_up" text
);
SELECT COUNT("no") FROM "alpg_tour_6" WHERE "margin_of_victory"='3 strokes';