Conversion from Sketchup to U3D is not supported yet :(

Sketchup

An SKP file is a three-dimensional model created by SketchUp, a 3D design program. It contains a model with wireframes, shades, edge effects, and textures.

The SKP file enables conceptual designs to be created, viewed, and shared quickly and easily. When you create a new document and save it in SketchUp the SKP file is created to store the document and its contents. SKP files can also be used to store SketchUp components. Components may be made by you or another user and can be imported into an SKP document to be inserted into your model.

U3D

Universal 3D (U3D) is a compressed file format standard for 3D computer graphics data.

The format was defined by a special consortium called 3D Industry Forum that brought together a diverse group of companies and organizations, including Intel, Boeing, HP, Adobe Systems, Bentley Systems, Right Hemisphere and others whose main focus had been the promotional development of 3D graphics for use in various industries, specifically at this time manufacturing as well as construction and industrial plant design. The format was later standardized by Ecma International in August 2005 as ECMA-363.

The goal is a universal standard for three-dimensional data of all kinds, to facilitate data exchange. The consortium promoted also the development of an open source library for facilitating the adoption of the format.