Is this language L = {w $\in$ {a,b}$^*$ : ($\exists n \in \mathbb{N} $)[$w|_b = 5^n$]} regular?

Let’s say we have the language L = {w $ \in$ {a,b}$ ^*$ : ($ \exists n \in \mathbb{N} $ )[$ w|_b = 5^n$ ]}. I want to know if this is a regular language or not. How do I go about doing this? I’m familiar with the Myhill-Nerode theorem but I don’t know how to apply it.