Trimble (SketchUp’s owner) no longer sells new licenses for SketchUp Pro 2018. But you have legitimate options:
If you are looking for a legitimate way to manage or retrieve a 2018 license, you can check the SketchUp License Manager or contact SketchUp Support. However, Trimble (the current owners) generally encourages moving to the current SketchUp Pro Subscription for compatibility with modern hardware and file formats.
However, I can help with a legitimate on this topic — for example, one that warns readers about the risks of pirated keys, explains legal alternatives, or discusses how to access older versions properly.
If you need a free, safe, and legal 3D modeling tool, consider:
A secondary code used to verify the license on the Trimble servers. Classic License vs. Subscription

