Vectors - Projection Lengths

The equation of line \(l\) is given by \(\mathrm{r}=\left( \begin{matrix}2\\1\\0 \end{matrix}\right)+\lambda \left( \begin{matrix}1\\-2\\1\end{matrix} \right)\). The coordinates of points \(A\) and \(B\) are \(\left( 1,3,-2 \right)\) and \((1,0,-2)\). Find the length of projection of \(\overrightarrow{AB}\) on \(l\).