If you cannot find a key, do not despair. SCS Software has essentially released the content as the for Euro Truck Simulator 2 (ETS2).
A (or serial key) is a unique alphanumeric code used to verify that your copy of the game is genuine. For STDS, this key is essential for unlocking the full version of the game after downloading the trial. How to Activate Your Game scania truck driving simulator the game product key