If using the above software doesn’t interest you, or doesn’t convert the files you want, is it still possible to obtain MP3 versions? Yes, but it does require some work. It can all be done using iTunes, so make sure you have some blank CDs handy. To help with this next section, I've added a series of screenshots. You can enlarge them by clicking on them at any point.

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First thing you want to do is to create a new playlist for your CD. From File, choose New Playlist. Give a name to your playlist, and then start selecting some files you want to burn. You can do this by holding on to the Control key while clicking tracks. Or, if you have a series of tracks in a row, you can highlight them by holding Shift and pressing either the Up or Down key, depending on the direction you want to go (after clicking the first in a series of tracks you want to highlight). Once you’ve chosen the files you want, right-click on one of the highlighted tracks, and highlight Add to Playlist, then choose the playlist you’ve recently made.
Go to your playlist, and check that all the files you want are there. You’ll now notice that on the bottom-right of the window, there’s an option that says Burn. Click that to open up another window. From here, be sure that the Audio CD option is checked before continuing. You can also modify the writing speed, as well as other options, such as the length of gaps between tracks. Then choose Burn.

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After your CD is burned, go to Edit, and then Preferences. 
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Make sure that the first tab on the left, General, is selected. Now, go down to the area that says When You Insert a CD. To the right of your option, there’s a button called Import Settings. Give that a click.
The top option, Import Using: choose MP3 Encoder. You can then choose the appropriate bit rate in Setting. Then click OK.