Theo Brightstart, the gnomish farmer wants you to move five boulders from his field into his farm cart. He will pay you 50 to 100 gold for your efforts. This requires at least 12 strength and will take up almost your entire inventory space. If you aren't strong enough, then you can use strength buffs like Elixir of Physical Prowess, Alcohol, Strength of Earth spell, etc.
In order to get this quest, you must first complete the Kill the Wild Pigs quest for Theo.