The D dominant thirteenth chord is a 6-note chord consisting of the notes D, F#, A, C, E and B.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as D13.
Chords that are a subset of D13. These contain less notes but all of them are included in D13.
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 D13 chord. Feel free to save or share the image as needed.