Special text-to-speech synthesizers exist that allows users to create an audio (like .mp3 file) with a speech from a saved text file, or document but they are usually pretty expensive. And even that will in most cases require manual tweaking during the process because otherwise the audio would not be perfect.
However, you most likely won't find a simple doc to mp3 conversion that does the job with a single click.
Unfortunately, there is no detailed software record in the database that match this conversion.
DOCX
Files with docx file extension are documents written and saved using Microsoft Word word processor edition 2007 or later. DOCX format replaced the previously used DOC format, moving from a binary files to Open XML schema based documents. Supported in almost every modern word processing tools.
MP3
The mp3 file extension is traditionally used for one of the most common type of compressed audio files MP3s, which you can playback using almost any media player.