I just went to check, & found this:
_You can convert compressed AAC, MP3, and Apple Lossless audio files by doing one of the following:_
• Select the audio regions pointing to the desired audio file in the Arrange area, then choose +Audio > Convert Regions to New Audio Files+ in the local Arrange area menu (or use the +Convert Regions to New Audio Files+ key command; default: Option-Command-F).
The part of the audio file spanned by the audio region is converted to a new audio file.
• Select the audio files in the Audio Bin, then choose +Audio File > Copy/Convert File(s)+ in the local Audio Bin menu (or use the +Copy/Convert File(s)+ key command).
+Important: Compressed audio files protected by the DRM (Digital Rights Management) scheme can not be opened in Logic Pro. Music bought in the iTunes Store is usually protected by DRM.+