The revenue function is
$$ R(p) = p\cdot q = 1000p(p+2)\exp(-p) $$
The revenue is maximized when $R^\prime (p)=0$, that is,
$$ -1000(p^2 - 2)\exp(-p)=0 $$
Since $\exp(-p)$ will never vanish completely, the revenue is maximized when $p=\sqrt{2}$, as the price cannot be negative.
You may also want to conduct a second derivative test to ensure that it is indeed the (local) maximum.