If you have no idea on where to go after reaching the Laugh Floor and defeat all of the enemies in the Monsters, Inc. world. You probably skip one of the scenes that’s why you have no clue on where to go next. The objective on this stage is “Grand on the door and head to the vault”.
To complete this objective, you just have to find the correct door. The correct door is found just inside the Laugh floor on the corner where there is a control panel.
Go to the Yellow door and press Triangle. It then prompts you to go to the door vault. Just select “Okay, let’s go!”
That’s it! Hope this helps you clear the stage.