Chemical Equilibrium

For the formation of ammonia from its constituent elements ( 1 mole of $\mathrm{N}_2$ and 3 moles of $\mathrm{H}_2$ ) in a closed vessel of volume $V(\mathrm{~L})$, the value of $K_C$ is [units of $K_C=\mathrm{mol}^{-2} \mathrm{~L}^2$ ]