Answer
$
\mu_{\mathrm{orb}, z}=-2.78 \times 10^{-23} \mathrm{~J} / \mathrm{T} .
$
Work Step by Step
Using Formula, we find
$$
\mu_{\mathrm{orb}, z}=-3 \mu_B=-2.78 \times 10^{-23} \mathrm{~J} / \mathrm{T} .
$$
That these are acceptable units for magnetic moment is seen from formula they are equivalent to $\mathrm{A} \cdot \mathrm{m}^2$.
