Which Template Files Do Page Posts Uniquely Rely On?

I just ported my site over to a new theme, and the front page and single blog post pages both look great.

https://www.vegan.com/
https://www.vegan.com/?p=80

Unfortunately, I’ve got a train wreck when I open any Page post (as opposed to blog posts, which show up fine).

https://www.vegan.com/?page_id=81

I’m quite new to WordPress, but I’m guessing the above meltdown must be occurring because in customizing my theme, I must have unknowingly corrupted a template file that Page views rely on, but nothing else does. Can somebody tell me which Template files are unique to a Page view? I’d like to replace these Template files with my theme’s original files.