Answer
$33 \pi \ in.$
Work Step by Step
Let $l$ be the length of an arc:
$l=\dfrac{\text{Measure of the arc}}{360^{\circ}} \times 2 \pi r ~~~(a)$
or, $l=\dfrac{\text{Measure of the arc}}{360^{\circ}} \times \pi d~~(b)$
Here, $r$ represents radius and $d$ is diameter.
$360^{\circ}-390^{\circ}=330^{\circ}$ and $d=36 \ in$
Thus, equation (b) becomes:
$l=\dfrac{330^{\circ}}{360^{\circ}} \times \pi (36)=33 \pi \ in.$