Step 1: Understand the question.
We want the speed of electromagnetic waves, like light, traveling through empty space. This speed comes from two properties of vacuum.
Step 2: Name the two constants.
One is $\mu_0$, the magnetic permeability of free space. The other is $\epsilon_0$, the electric permittivity of free space. They describe how vacuum carries magnetic and electric effects.
Step 3: Write the speed formula.
From Maxwell's equations the wave speed is \[ c = \frac{1}{\sqrt{\mu_0\epsilon_0}} \]
Step 4: Check the units idea.
Taking the inverse square root of the product gives a speed, which matches the value of the speed of light. The other forms do not give a speed.
Step 5: Rule out the wrong forms.
The plain product $\mu_0\epsilon_0$ or its square root do not give the right value, and $1/(\mu_0\epsilon_0)$ is the square of the speed, not the speed itself.
Step 6: State the answer.
The speed of electromagnetic waves in vacuum is the inverse square root of $\mu_0\epsilon_0$. \[ \boxed{c = \frac{1}{\sqrt{\mu_0\epsilon_0}}} \]