The most convenient way to convert mp3 audio to caf format would be to use iTunes. You can use Apple iTunes to convert MP3 to Apple Core Audio Format (CAF) using the following procedure. Open Edit menu ► Preferences ► Import settings ► Set Import Using to AIFF Encoder ► Ok button ► Right click on MP3 file ► create AIFF version.
Other than that, it is very likely that other audio programs with support for Apple Core format can be used for the purposes of mp3 to caf conversion.