"SketchUp version 1800"

There is no official . It is likely a typo for SketchUp 2018 (specifically version 18.0 ). While SketchUp 2018 is no longer the latest release, you can still access newer official free options or locate older versions through archives. Official Free Versions (Recommended)

To ensure you have the latest and most secure version, use the following official links:

Here is what you are likely to actually download instead of a working 3D modeler:

Q2: Will my old plugins work with Version 1800?

Most plugins created between 2014 and 2019 (RBZ files) will work. Install via Window > Extension Manager . However, V-Ray 5 or Enscape 4 will not—they require SketchUp 2021+.