Use the Empty Termite Jar on the Termite Mounds in Eastern Plaguelands. After you've gathered 100 Plagueland Termites, return to Mickey Levine at the Bulwark in Tirisfal Glades.
So, to bring pain and strife to the Scarlet Crusade, I want to take their precious lumber mill from them. I'm sure the loss of such a resource will cause them a great deal of harm in defending and rebuilding the town for their own reasons. Will you help me, [player]?
Start by taking this jar to Plaguewood in the Eastern Plaguelands. Fill it with the termites you find in their mounds throughout the woods. Come back when you have enough.