m4a to jpg conversion can actual mean several things, but neither of these is common or audio conversion. In most cases it is searched by users that are looking for a way to convert out the thumbnail image from the MPEG-4 container or replace it. Various multimedia editors can be used for this.
Updated: September 27, 2023
Unfortunately, there is no detailed software record in the database that match this conversion.
M4A
Files with m4a extension are audio files stored in MPEG-4 (MP4) container and use AAC (Advanced Audio Coding), or Apple Lossless (ALAC) audio compression. M4A is very popular on Mac computers, because it is default audio format used by iTunes. M4A is also default audio format for Apple portable devices (iPod, iPhone, iPad).
JPG
Files with jpg file extension contain pictures, digital photos, and other bitmap images. It is one of the most common image formats used today.