Follow the steps below to convert WMV 3GP MP4 files to FLV.
Converting WMV 3GP MP4 to FLV using Mopal Video Converter
http://www.softe.net/video_converter.php
1. After launch Mopal Video Converter, In the folders pane, click on
the folder contains WMV 3GP MP4 files you want to convert to FLV.
2. In the file list pane, select one or more WMV 3GP MP4 files.
3. Right click on the selected WMV 3GP MP4 files to bring up the
context menu and select Convert.
4. In the Video Format Conversion window, select FLV from the Output-
>Format list.
5. If you want to change the output quality, select the video/audio
combobox. (optional)
6. If you want to change the destination folder for FLV, click on the
Browse icon button to change. (optional)
7. Click Convert to start converting.
http://www.softe.net/mopal_help/convert-wmv-flv.php