Explore the Fargodeep Mine, then return to Marshal Dughan in Goldshire.
The mine in Northshire isn't the only one with problems! I have reports that the Fargodeep Mine in Elwynn has also become a haven for Kobolds.
Explore the mine and confirm these reports, then return to me. The mine is almost due south of Goldshire, between the Stonefield and Maclure homesteads.