TEN POINTS TO THE BEST ANSWER

The ringtone I'm looking for is not available for purchase (I looked) so the only way I can have it as my ringtone is if I convert the mp3 file into a .dcf file. The problem is that I don't know how to do that, so if someone could tell me how or point me in the direction of someone or a website that would teach me how to do that, I would greatly appreciate it.

Thanks!