3-1

3-1 can refer to the following:
 * World 3-1 from various games
 * Level 3-1 from various games
 * Stage 3-1 from Donkey Kong for the Game Boy
 * Shriek Mansion 3-1 from Super Princess Peach
 * Room 3-1 from the Mario vs. Donkey Kong series
 * Chapter 3-1 from Super Paper Mario
 * Area 3-1 from Mario vs. Donkey Kong: Mini-Land Mayhem!