$\mathrm{NH}_3$ act as WFL with $\mathrm{Ni}^{2+}$
$$\mathrm{Ni}^{2+}=3 \mathrm{~d}^8
$$

No. of unpaired electron $=2$
$$
\begin{aligned}
\mu=\sqrt{\mathrm{n}(\mathrm{n}+2)} & =\sqrt{8}=2.82 \mathrm{BM} \\
& =28.2 \times 10^{-1} \mathrm{BM} \\
\mathrm{x} & =28
\end{aligned}
$$