The modulus of $ z $ is:
$$ |z| = 3 \sqrt{ 13 }$$To find modulus of a complex number $ z = a + bi $ we use formula:
$$ |z| = \sqrt{a^2 + b^2} $$In this example we have $ a = 9 $ and $ b = 6 $ so:
$$ \begin{aligned}|z| &= \sqrt{ 9^2 + 6^2 } \\[1 em]|z| &= \sqrt{ 81 + 36 } \\[1 em]|z| &= \sqrt{ 117 } \\[1 em]|z| &= 3 \sqrt{ 13 } \\[1 em] \end{aligned} $$