Use either imperial or metric units.
Without doing the math you will need a lot of weight to generate that amount of power. The bearing needed to support the pulley and the gearing needed to spin the generator will introduce significant friction.
I expect it is impractical. I was never good at this sort of problem but let me give it a shot anyway. Please feel free to correct me.
A HP is 33,000 foot-pounds of work in one minute.
You specified that your weight can drop 10m in 10hours which is 33 feet in 10 hours or 33/600 feet per minute. That is .055 feet per minute.
With a one foot pulley you would need a weight (33,000/.055) 600,000 lbs to get the needed 1 HP. With the weight moving at .055 ft/min it will turn the 1 foot pulley once in (3.14*1)/.055 = 57 seconds.
Even if I am off by a few orders of magnitude it is still impractical.
EDIT: Gravity is a weak force.