The orbital angular momentum ($L$) of an electron is determined by the azimuthal quantum number ($l$) using the formula: $L = \sqrt{l(l+1)} \frac{h}{2\pi} = \sqrt{l(l+1)} \hbar$

1. Identify Quantum Number: For a d-orbital, the azimuthal quantum number is $l = 2$.
2. Calculate Momentum: $L = \sqrt{2(2+1)} \hbar$ $L = \sqrt{6} \hbar$ $L = \sqrt{6} \frac{h}{2\pi}$

(Note: The input 'hhh' typically denotes the constant unit, often represented as $\hbar$ or $h/2\pi$ in this context).