OK, we got this working and it wasn't intuitive to me at least. I'm a true citizen developer and not a pro.
I had to use the "enter custom value" for the Site Pages

Pretty easy...but then the fun began as we wanted to see if people were updating their site pages for content in a certain area. So we then did a "get file content using path action" and looped through all the site pages. We stored the file content in a new variable (that was a critical step we thought)
On the original Get Files we also did a odata filter to tighten the array.

Then we used the expression indexOf to locate the "section header" in our document.
We then did an indexOf for the following section and calculated the difference using the sub expression between the index of both sections and we determined that if the difference exceeded 2800 then there is content in between else the person hasn't updated the section.
Before, someone was looking at all 70 pages manually to see if the section had been updated.
Now, they are emailed the pages that haven't been updated.
Pretty neat eh....