Try zamzar.com
1.copy the URL
2.then go to the website
3.click URL
4.Past URL
5.put what u want to convert it to
6.put email address
7. click CONVERT


i dont know if this will help but give it a try

You should download the video at first and then use a video converter to convert the format to mp3. There are various such programs, say handbrake, any video converter and so on. For a better use(because there is a big possiblity that some free ones may have limits of your vidoe size), i advise you this powerful video converter, video converter ultimate, and you can have more details if you want to know more.http://www.aimersoft.com/online-video/convert-url-to-mp3.html