Answer
$6 \pi$
Work Step by Step
Here, we have
$ ds=\sqrt {(\dfrac{dx}{dt})^2+(\dfrac{dy}{dt})^2+(\dfrac{dz}{dt})^2} dt$
and $ds= dt$
This implies that
$L=\int_{0}^{2 \pi} (\cos t -\sin t+3) dt$
Thus, $[\sin t+\cos t+3t]_{0}^{2 \pi}=6 \pi$