The D flat minor sixth chord is a 4-note chord consisting of the notes Db, Fb, Ab and Bb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Dbm6.
Chords that are a superset of Dbm6. The chords include more notes but always Db, Fb, Ab and Bb.
Chords that are a subset of Dbm6. These contain less notes but all of them are included in Dbm6.
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 Dbm6 chord. Feel free to save or share the image as needed.