Follow the steps as follow
1. Donwload Free Mobile Helper at http://www.macrobile.com/download/?r=129 and install it.
2. Connect your iphone 3GS with PC through WIFI or USB
3. Add your pictures and videos to PC. Free Mobilr Helper -- Home -- File Manager -- Video. Then you can see your videos on your old phone. Click the " Download to PC" button. You can select the file you place these videos.
4. Switch Device. Add the video to the new iphone. Free Mobilr Helper -- Home -- File Manager -- Video -- Upload -- Upload file or Upload folder. Then you can add the videos.
Transfer music is almost the same.