The commercial version of SketchUp supports export to several 3D/CAD formats - including the common 3D Object format (.obj.), hence allowing skp to obj conversion.
This can be achieved using the File ► Export ► 3D model function found in the program. When you export skp to obj, you need to define several settings, including settings for edges, textures, faces or units. Several limitations for this conversion exist, so before you convert skp to obj, it may be worthwhile to check SketchUp Help Center and read about the limitation of exporting skp to obj in first place.
Nowadays, may 3D modeling tools also support SketchUp formats and same goes for dedicated 3D converters, so you can perhaps perform this conversion with other programs as well.
Updated: June 21, 2023