How I can make a camera follow a route by pressing a button?

There is a package in the Asset Store called ORNavigation. And the script wiki is down, but there may be something there. If you can't find anything, what you do is define your route (somehow), and use a Slerp function to move the camera, using Update to listen for the KeyDown event you want. A simple way to define a route is have a list of 'waypoints' which can be empty game objects that you place along the route, then slerp the camera between them.