You are downloading the 3DVu XAP file v1.0.2.0 for Windows Phone. 3DVu is a free and useful Education app: 3DVu is a simple 3d model viewer with a built-in model library. Supported 3D models can be downloaded locally and viewed offline.Currently ... You can now download the offline XAP file to install & try it.
Download Locations for 3DVu 1.0.2.0 XAP file
To try to install it manually from an SD card, you should choose one of the server location above to get the offline 3DVu XAP file, move the file to your phone's SD card and then tap 'Install local apps' in the phone's App list.