Can you give year and model? That motor traces to 2007+ for me.. Want to make sure that's right. The big trucks have different connectors and I don't want to steer you wrong.
The OBD plug looks like this:
Indications that the Scan Gauge "D" from "Camping World" works with ISB 340 6.7L Cummins - via the round diagnostic port. Looks like your DP doesn't do OBD-II, which apparently is typical.. (and something I'm not that familiar with).