Oscillation vs. Pendulum Periods

[1MileCrash]

Homework Statement

The rotational inertia of a uniform thin rod about its end is ML2/3, where M is the mass and L is the length. Such a rod is hung vertically from one end and set into small amplitude oscillation. If L = 1.0 m this rod will have the same period as a simple pendulum of length:

Homework Equations

The Attempt at a Solution

My original plan was to use a system of equations with:

T = sqrt(I/k) (oscillation, where k is torsion constant)
and
T = 2pi(sqrt(L/g)) (simple pendulum.)

However, I don't know the torsion constant and have no means to find it. What's my first step?

 

[1MileCrash]

Should I get k in other terms and substitute?