Hi SharonRB,
This can be done but it's a pain. I hate iTunes but I have to use it for my iPhone. Anyway, here's what you do.
You'll need a cheap or freeware mp3 ripper program that you can download on the net and install it on your computer (regardless of whether you've got a PC or a Mac)
You need to create an audio (standard music CD as opposed to an MP3 disc) CD with the songs that you bought on iTunes. It can't excede 70 minutes worth of music (a limitation of the standard audio CD).
Once the CD is completed, open the CD tray but leave the CD in it - don't close it yet.
In iTunes, Choose Edit/Preferences/Advanced tab/Importing tab
Change 'Import using:' to MP3 Encoder.
You can change the setting to something higher if quality is really important to you - I listen to a lot of classical so it is to me. If you listen to mostly 'radio/popular' you can leave the default setting.
Close the dialog box/window.
Close CD tray now.
iTunes will ask if you want to import the songs. Say yes.
(If you made the CD as an exact copy of an existing CD with all the same songs in the same order as the original album, iTunes may recognize it and name it properly. If not, you'll have to rename every song so that you'll recognize it.)
iTunes will now import all the songs on the audio CD as mp3 files.
Repeat this process untill you've got all the songs you want to put on an mp3 CD. If you chose 'high quality (320Mhz)' on the settings, you can get about 4 audio CD's worth of music on one mp3 CD. If you chose a lower quality, you can get more than that. The lower the quality, the more songs you can get on one CD.
Then you will need to burn the mp3's onto a CD with an application other than iTunes (like Roxio.)
I hope this helps.
P.S. The audio CD will play fine in the car, it just hold's at best, only a quarter of the music that an mp3 CD can hold.