Welcome aboard to the forum
Unfortunately, as Apple does not license out its FairPlay DRM technology, only Apple supply equipment and software that can play its store's music, such as its iPod player & phone series, iTunes software, etc. However, there are several ways you can go about converting your music to MP3 tracks.
Probably the simplest way is to get a highspeed CD-RW: Use iTunes to record as many iTunes songs that will fit to CD and then rip the written CD to MP3 tracks. The advantage with using a CD-RW for this is that it can be erased and reused to process another group of songs. The catch is the slow tedious writing and ripping process, not to mention possibly having to manually name each song also.
Tunebite is quite a popular software tool for converting copy protected tracks to MP3, however the tool is not freeware.
Finally, if you are familiar with how to convert non-protected AAC music to MP3 (excluding iTunes), you could try using the
hymn-project to strip the DRM from your music. Unfortunately, as the last software update was July 2004, it is not clear if this software still works with recent iTunes music. If this tool does work fine, you will need to use some other conversion tool other than iTunes to re-encode the tracks to MP3, since
iTunes is known to put DRM back on iTunes purchased tracks that are missing it!
Good luck
