The supported formats differ, depending on how you use the CDJ-3000. Refer to the sources below for details, which might change according to updates.
■ USB Storage Device/rekordbox (Export mode)
See [Supported File Formats] in [Product overview] in the Instruction Manual.
The Instruction Manual is available [here].
■ rekordbox (iOS)
See [here] [Supported file formats] in [rekordbox(iOS) in System Requirements.
■ rekordbox (Performance mode)
See [Music files that can be loaded and played (file formats)] in the rekordbox Instruction Manual.
You can read the rekordbox Instruction Manual [here].