Buy a cow pasture (level 6, 15 min) from the Marketplace. You will get 2 milk's once the pasture is done building. After that then it takes 5 oats and 2 min to get milk from the cows. You can sell any 3 goods to Myra for the last task on this quest.
As soon as you finish this quest, the next quest, Skimming the Cream, begins