The "html" is in literally THOUSANDS of places - all in tiny little "pieces" mostly - and practically all of it is shrouded in PHP CODE.
What you see on your browser screen (when you VIEW PAGE SOURCE), is just the RESULT of the php CONSTRUCTING that page, from all the myriad of resources it gets information from.
There are no "HTML" pages in a dynamic content website. ALL pages are cobbled together by the code, and then delivered to the browser screen. When the viewer clicks a link, or performs an action (eg: add to cart), the page they are on EVAPORATES FOREVER... and a brand new page is built up on-the-fly by the PHP. Any click on a page makes it vanish forever, and a new page is built in its place....
... along the way, calculations can be performed, data captured, and specified conditions "tested" (eg: the visitor can only do this of they are logged in).
So... if you are looking for the HTML, it is there... but not in the format you are expecting it to be...