Using the Law of Conservation of Energy to Find Speed?

[michelle]

A 500.0 kg pig is standing at the top of a muddy hill on a rainy day. The hill is 100.0 m long with a vertical drop of 30.0 m. The pig slips and begins to slide down the hill. What is the pig's speed at the bottom of the hill? (Use the law of conservation of energy).

I believe I would need to use the following equation:
?KE = ?PE
which is written out as:
(1/2)mvo^2 + mgho = (1/2)mvf^2 + mghf
m = mass
vo = original velocity
g = acceleration due to gravity (I use 9.81)
ho = original height
vf = final velocity
hf = final height

So how do I go about plugging everything in? Especially for velocity... ?