Start by forming an equation relating radius, height, and surface area, and fill in the known quantities.
Break the object up into two-dimensional surfaces: two circles (top and bottom) and a rectangle (wrap around)
Area of a circle = pi * r^2
Area of a rectangle = base * height
this is tricky though because the base is supplied by the circular circumference (2 * pi * r)
If you combine these properly, the result should be equal to surface area, and be determined by radius and height. After that, it is just a matter of plugging in known variables and solving.