Modulus of a Complex Number

Consider the complex number defined by $z = 3 + 4i$. In this expression, $i$ represents the imaginary unit, which is defined by the property $i^2 = -1$.

Calculate the modulus of the complex number $z$. The modulus of a complex number $a + bi$ is calculated using the formula: $$|z| = ext{sqrt}(a^2 + b^2)$$ where $a$ is the real part and $b$ is the imaginary part of the complex number.

Provide your answer as a decimal.