Videos in Facebook can be added by mobile device or uploaded directly. If you have added or uploaded videos in Facebook, then you have the record of it. But if someone has added it which you think is very good one and should be kept an audio file of it with you, then converting of the video to a Mp3 file is mandatory.
Taking the fact into consideration, an application is available on net to get you through this and make it possible for you.
The "Fb2mp3" application is one such way to convert any videos on Facebook to mp3 format.
The service is fast, secure, free and requires no sign up to convert the video file into audio file. The only requirements are the URL of the Facebook video and the software of the application with you that will transfer the files, convert them and give you a link to download the audio file.
Select the option "Standard Quality" and click "Go".
In few moments, your video will get converted into an audio mp3 file.
Note: Once you click on "Go" option, your file needs some time to get converted to mp3 format. Later you will be given a download link of audio file.