The modulus of $ z $ is:
$$ |z| = \frac{ 5 }{ 2 }$$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 = 2 $ and $ b = -\frac{ 3 }{ 2 } $ so:
$$ \begin{aligned}|z| &= \sqrt{ 2^2 + \left(-\frac{ 3 }{ 2 }\right)^2 } \\[1 em]|z| &= \sqrt{ 4 + \frac{ 9 }{ 4 } } \\[1 em]|z| &= \sqrt{ \frac{ 25 }{ 4 } } \\[1 em]|z| &= \frac{ 5 }{ 2 } \\[1 em] \end{aligned} $$