List the number of tournament winners when iona , siena & niagara won in the regular season.
CREATE TABLE "table1_24348134_3" (
  "conference" text,
  "regular_season_winner" text,
  "conference_player_of_the_year" text,
  "conference_tournament" text,
  "tournament_venue_city" text,
  "tournament_winner" text
);
SELECT COUNT("tournament_winner") FROM "table1_24348134_3" WHERE "regular_season_winner"='Iona , Siena & Niagara';