M = mass of earth (look it up in kg)
G = universal constant of gravitation (look it up in Nm2/kg2)
h = altitude of orbit (given, but convert to meters)
Assuming a circular orbit of radius r,
v2 / r = GM / r2
v2 = GM / r
v = √(GM/r) = √[GM / (Re + h)]
Plug in the numbers (with h in meters) and get v in m/s.