Answer
The pressure amplitude increases by a multiple of $~~32$
Work Step by Step
In part (a), we found that the sound intensity increases by a multiple of 1000.
We know that: $~~s_m^2 \propto I$
Thus $~~s_m \propto \sqrt{I}$
Then: $~~p_m \propto s_m \propto \sqrt{I}$
Note that $\sqrt{1000} = 32$
The pressure amplitude increases by a multiple of $~~32$.