The modulus of $ z $ is:
$$ |z| = \sqrt{ 6229 }$$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 = 73 $ and $ b = -30 $ so:
$$ \begin{aligned}|z| &= \sqrt{ 73^2 + (-30)^2 } \\[1 em]|z| &= \sqrt{ 5329 + 900 } \\[1 em]|z| &= \sqrt{ 6229 } \\[1 em] \end{aligned} $$