Answer
See below
Work Step by Step
If $P = P_1P_2 ... P_k$, where each $P_i$ is an elementary permutation matrix
then $P_i=P_i^{-1}=P_i^T$
Thus, $P^{-1}\\=(P_1P_2..P_k)^{-1}\\=P_k^{-1}...P_2^{-1}P_k^{-1}\\=P_k^T....P_2^TP_1^T\\=(P_1P_2...P_k)^T\\=P^T$