Programs enabling conversion of the file:
If your objective is to convert the file from 3GP to the file DVR-MS, you can use any of the applications listed. 3GP to DVR-MS conversion process in every program intended for this purpose (so-called converters) is very intuitive and everyone is able to manage converting a file.
However, bear in mind that the list may also include programs to support and work with the indicated extensions 3GP and DVR-MS - and not only converters. In such a case, you need to open the source file 3GP and from the options available in the program, choose ”Save as... DVR-MS" or "Export to DVR-MS".