This guide will show you how convert you audio files with iMoviesoft Audio Converter.
Steps:
step 1. Download and install iMoviesoft Audio Converter

step 2. Add Videos/Audios.
There are two methods for you to add videos/Audios:

step 3. Select your aiming Profile and Output Folder for your audio
step 4. Click “Start” button to begin the conversion.
Tips: You can pause, stop and continue smoothly when converting.
Further Edit:
Two ways for trim
You can adjust different parameters of audio including Channel, Sample Rate, Channel, Audio Bitrate, Audio Codecs
Besides above edit functions, you can merge several audios into one output file.
Hopefully you can enjoy your videos on your iPhone with the help of iMoviesoft Audio Converter
Related tutorial:
How to Convert Your Audio like MP3 to AAC, AAC to AC3, MIDI to WAV, etc on Mac?