Answer
$$\| v \| =\sqrt{6}.$$
$$\frac{1}{\| v \|}v=\frac{1}{\sqrt{6}}(1,-2,1)$$
Work Step by Step
Let $ v=(1,-2,1)$, then we have
$$\| v \| =\sqrt{\langle v, v\rangle}=\sqrt{v_1^2+v_2^2+v_3^2 }=\sqrt{6}.$$
The unit vector in direction of $v$ is given by
$$\frac{1}{\| v \|}v=\frac{1}{\sqrt{6}}(1,-2,1)$$