It's called "audio to midi" and can be found in the sample/audio editor. Works rather well on "only rhythmic" stuff, ok-ish on some monophonic material, not at all for polyphonic signals.
If you want/need to do this more often, and more or less stay inside Logic, Melodyne with it's new DNA feature might be worth a try. Not only does it a rather excellent job of extracting MIDI from monophonic audio, meanwhile this also works for polyphonic signals (mind you, they still need to be rather clear signals). Not exactly a cheap solution, but probably the best there is on the market.