The B flat minor thirteenth chord is a 6-note chord consisting of the notes Bb, Db, F, Ab, C and G.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Bbm13.
Interactive piano diagram for the B flat minor thirteenth chord
Chords that are a subset of Bbm13. These contain less notes but all of them are included in Bbm13.