It's not marked on the map, but you should be able to find it without too much trouble. You can find a shovel lying on the cart right next to the mill. Unfortunately, the actions the miller requires of you are not exactly. Peshek wants you to repay the money he's had to spend on herbalist appointments and whatnot, and if you want to be debt-free in 1403, you should get Peshek off your back ASAP. It seems you've racked up quite the debt by lying unconscious in his mill the past two weeks, which doesn't exactly seem fair, but then it is the Middle Ages. Once you've finished the intro and gathered your things, go and talk to Miller Peshek, who will give you this multi-part quest. This will likely be the first side quest you come across, unless you flee from Rattay immediately after waking up there.
