1. Press and hold the Power button on your 3DS until the system turns off.
2. Open the game card slot and remove the Nintendogs + Cats: Toy Poodle 3DS game card.
3. Reinsert the game card into the game card slot and close it.
4. Turn on your 3DS and start the game. Your game should now be reset.
Please note that this will delete all of your saved data, including your dogs and cats. Make sure to back up your data before resetting your game.