I have a strange question. Its been almost a year I have

I have a strange question. Its been almost a year I have been developing in WP and I find one small/big problem: finding the right file to change.

Basically, is there a way (using inspect element, a plugin for wp, another idea) to find the right file that is used to display content on the front end? For example, this page on my last project:

http://mokabox.tv/jeff/videos

displays a list of videos. I cannot find this page to I can update the design. I looked everywhere (I think) and I just cannot find it. Between all the plugins, custom functions and themes I am lost!

Thanks for any advice/suggestions.

Jeff