The primary way to get a legitimate key is by purchasing a license through official or authorized channels.
A simple Google search for will yield thousands of results promising "keygens," "cracks," or "free serial numbers." While the temptation to save money is understandable, pursuing these avenues comes with significant risks.
Visit the Steam Exchange Portal to convert your serial number.
The primary source for the game is the official . By buying directly from the developer, you usually receive the key instantly via email. This also guarantees you are getting the most up-to-date version of the simulator.
Modern versions of City Car Driving (1.5.x and above) use online server-side verification. This means the software checks the key against a master database. If 1,000 people try to use the same "free" key found on a blog, the server immediately blacklists that key.