The B flat minor ninth chord is a 5-note chord consisting of the notes Bb, Db, F, Ab and C.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Bbm9.
Chords that are a superset of Bbm9. The chords include more notes but always Bb, Db, F, Ab and C.
Chords that are a subset of Bbm9. These contain less notes but all of them are included in Bbm9.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the Bbm9 chord. Feel free to save or share the image as needed.