The modulus of $ z $ is:
$$ |z| = \frac{\sqrt{ 2117 }}{ 50 }$$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 = -\frac{ 1 }{ 50 } $ and $ b = \frac{ 23 }{ 25 } $ so:
$$ \begin{aligned}|z| &= \sqrt{ \left(-\frac{ 1 }{ 50 }\right)^2 + \left(\frac{ 23 }{ 25 }\right)^2 } \\[1 em]|z| &= \sqrt{ \frac{ 1 }{ 2500 } + \frac{ 529 }{ 625 } } \\[1 em]|z| &= \sqrt{ \frac{ 2117 }{ 2500 } } \\[1 em]|z| &= \frac{\sqrt{ 2117 }}{ 50 } \\[1 em] \end{aligned} $$