This quest is not available in game.
Thrall wants you to return to Gorkan Bloodfist at Mag'har Post in Hellfire Peninsula and offer him your services.
I'd leave for Outland this very minute after hearing the news you brought. Important matters require my attention in Durotar, however.
I will arrange for a fitting tribute to be sent to the Mag'har immediately. I will send my most trusted diplomats as well. This will all take time... I need someone to represent us there right now.
I must place my trust on you, <name>. Go to the Mag'har Post in Hellfire and render whatever services you can to my kin. Do not fail me, <name>. Too much depends on this.