Converting Purchased AAC files to mp3

Music sold on the iTunes Store has not been protected by DRM for many years now and has always been only available in the AAC format. The iTunes app has the ability to convert music from one format to another e.g. from AAC to MP3. To convert format in iTunes see Convert a song to a different file format with iTunes - Apple Support

iTunes will leave the original format in the iTunes library and add the new converted format, as a result and as hhgttg27 was demonstrating you will end up with both versions listed. iTunes also helpfully converts the meta-tag information. You can go to the View menu and enable an additional column which will show which format a track is in, or you can select a track and then right-click and select Get Info.

These days there is very little reason to convert to MP3 format. Windows has supported AAC format for a number of years, obviously all Apple devices i.e. iPhone, iPad, iPod, Apple TV support AAC but so do many other devices and programs.

I can't reproduce this - when I convert a Purchased AAC to MP3 I see both versions in my library:

If I then add the MP3 version to a playlist it stays as MP3:

My best guess is that you're actually adding the original AAC track and not the MP3 version - are you working in a playlist when you perform the conversion? If so, note that only the original track is associated with the playlist, the converted one can only be located in your library.

I have to ask - if you want your media in MP3 format why not purchase it from retailers that deliver this, rather than having to go through a conversion process that inevitably leads to quality loss?

You can't specify the file format when purchasing from iTunes. What hhgttg27 was saying is that if you want your music in MP3 format, you can purchase it from other online sellers that sell their music in MP3 format, such as Amazon MP3.