\(I = {I_{CM}} + M{d^2}\)
Where \({I_{CM}}\) is the moment of inertia of the given rod about an axis passing through its center of mass and perpendicular to its lenght and \(d\) is the distance between two parallel axes.
Herer, \({I_{CM}} = {I_{0'}}\,d = \frac{L}{2}\)
\(\therefore \,I = {I_0} + M{\left( {\frac{L}{2}} \right)^2} = {I_0} + \frac{{M{L^2}}}{4}\)