Download iTunes from itunes.com and install it. Then open iTunes.
Click "File," then "Preferences" to open the "Preferences" menu.
Click the "Import Settings" button.
Click the "MP3 Encoder" as your audio conversion format.
Click the "Settings" menu and click "Custom."
Click the "Stereo Bit Rate" drop-down menu and click "320 kbps." This will be the highest bit rate available in the menu.
Click "OK" to confirm these changes and exit the "Preferences" menu.
Drag the audio files into iTunes that you want to make MP3s out of.
Highlight these audio files, and then click "Advanced" and click "Create MP3 Version." After doing so, MP3s with the best sound quality possible will appear below the original audio files.
Download Switch from nch.com.au and install the program. Open Switch.
Click "Add Files" and select the audio files you want to make MP3s out of.
Click ".mp3" as your audio conversion format from the "Output Format" menu.
Click the "Encoder Options" button.
Click the "Bitrate" drop-down menu and click "320 kbps." This is the highest bit rate available in the menu.
Click "OK" to confirm these changes and exit the "Encoder Options" menu.
Click "Browse" to select where you want to save your high quality MP3s on your computer.
Click "Convert" and your audio files are converted to MP3s with the best sound quality possible and saved in the output folder you selected.
Download the dBpoweramp program from dbpoweramp.com and install it. Open dBpoweramp.
Click "Browse" and click the audio files you want to make MP3s out of.
Click "MP3" as your audio conversion format from the "Converting To" menu.
Drag the "Estimated Bit Rate" slider to the far right to select "320 kbps." This will be the highest bit rate available on the slider.
Click "Folder" to select where you want to save your high quality MP3s on your computer.
Click "Convert" to convert your audio files to MP3s with the best sound quality possible and save them in the selected the output folder.