How to change scenes for a racing game.

I have created 2 racing tracks and i want to change the scene when the player’s car reaches 3 laps.I am using ctrl-j’s jcar project and i have managed to create 2 extra tracks and cars on different scenes.I am still learning unity3d ,so i am just playing around with the different tutorials and projects to see how they work.

I don’t know about that project, but take a look at that.