Answer
$9p^4-6p^3+p^2$
Work Step by Step
Using $(a+b)^2=a^2+2ab+b^2$ or the square of a binomial, the given expression, $
\left( 3p^2-p \right)^2
$, is equivalent to
\begin{array}{l}\require{cancel}
(3p^2)^2+2(3p^2)(-p)+(-p)^2
\\\\=
9p^4-6p^3+p^2
.\end{array}