Nested project pages

I believe this is a simple question for an advanced designer (which I’m not). On my site I have 6 CMS collections (Practice Areas), and each collection is displayed on it’s own Practice Area page.

How do I create a navigation sequence like this:

https://www.homepage/portfolio/‘practice-area’/'CMS project page’

I’ve built the first 2 levels of navigation, but the last level befuddles me…

Here is my site Read-Only: