WRF to MP4 conversion is typically related to export of WebEx web conference video (.wrf) to MPEG-4 video (.mp4) files.
The most convenient way to achieve this conversion is to download the latest version of Cisco WebEx a program that allows free export to several multimedia formats including WMV, SWF and possibly MP4 format. The program is available for both Windows and macOS.
You can also use WebEx Recording Editor for some simple edits of .wrf files prior the export to MP4 or other supported multimedia format.
Should the export to MP4 format does not work for you for some reason, you can always save it as WMV (Windows Media Video) and use any of the available wmv to mp4 converters to get your .mp4 file.