Answer
$I \approx 1.2 \times 10^2 \mathrm{~W} / \mathrm{m}^2$
Work Step by Step
The intensity of the wave is
$
I=\frac{E_m^2}{2 \mu_0 c}=\frac{(300 \mathrm{~V} / \mathrm{m})^2}{2\left(4 \pi \times 10^{-7} \mathrm{H} / \mathrm{m}\right)\left(2.998 \times 10^8 \mathrm{~m} / \mathrm{s}\right)}\\=119 \mathrm{~W} / \mathrm{m}^2\\ \approx 1.2 \times 10^2 \mathrm{~W} / \mathrm{m}^2
$
