MP4, also known as "MPEG 4" is one of the most common formats for digital video files. "MP4" stands for "Moving Pictures Expert Group 4", which is a standard for audio and video coding compression.
If you are looking to convert video audio files to MP4, you can use free video players like VLC player that support formats including MP4, MPJPEG, MPEG-2, PS, and PVA. Be sure to check what desired output format you would like to target as well as the original file size before you begin conversion.
When you convert the video to the MP4 format, be sure to take a step-by-step approach when you select and save to a particular format during the file conversion process.