MP3 vs MP4 - Difference Between The Two File Formats
Amazon.com: TIMMKOO 72GB MP3 Player with Bluetooth, 4.0" Full Touchscreen Mp4 Mp3 Player with Speaker, Portable HiFi Sound Mp3 Player with Bluetooth, Voice Recorder, E-Book, Supports up to 512GB TF Card (Black) :
FREE | How to Convert MP3 to MP4 on Windows 10/Mac/Online - EaseUS