The modulus of $ z $ is:
$$ |z| = \frac{ 13 \sqrt{ 5}}{ 5000 }$$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{ 13 }{ 2500 } $ and $ b = \frac{ 13 }{ 5000 } $ so:
$$ \begin{aligned}|z| &= \sqrt{ \left(\frac{ 13 }{ 2500 }\right)^2 + \left(\frac{ 13 }{ 5000 }\right)^2 } \\[1 em]|z| &= \sqrt{ \frac{ 169 }{ 6250000 } + \frac{ 169 }{ 25000000 } } \\[1 em]|z| &= \sqrt{ \frac{ 169 }{ 5000000 } } \\[1 em]|z| &= \frac{ 13 \sqrt{ 5}}{ 5000 } \\[1 em] \end{aligned} $$