Originally Posted by Jellby
They are all inside the epub. Unzip the epub (or open it with Sigil) and you'll get your raw files inside. There's nothing arcane about that, an epub file is simply a bunch of text files (not necessarily ASCII, could be utf8 or utf16) zipped with a specific structure.
But Hitch's answer is much more complete, go back and read it if you have been intimidated by its length at first
Too many years wrangling massive real estate development deals with thousands of pages of documents--I over-explain. Old adage: "tell 'em what you're gonna tell them, tell them, then tell them what you told them." Unfortunately, in this day and age, that much exposition seems not to be popular. ;-)