Answer
Please see the work below.
Work Step by Step
We know that
$V=\frac{4\pi r^3}{3}$
This simplifies to:
$r=(\frac{3V}{4\pi})^{\frac{1}{3}}$
We plug in the known values to obtain:
$r=(\frac{3(4.418\times 10^{-23})}{4\pi})^{\frac{1}{3}}=2.193\times 10^{-8}cm$
The conversion of units is made as follows
$2.193\times 10^{-8}cm\times \frac{1\times 10^{10}pm}{1cm}=219pm$