When it comes to producing a Kindle e-book for publication, you can find convertors that will take a Word document and convert it into a file that will work, sort of. But, I don’t recommend it. If you truly want your book to read and look professional in every way, you should hand code your book.
Why go to the trouble, or expense? Because it matters to the reader and isn’t very professional. Bad formatting distracts from the reading experience and can become frustrating when built in features do not work, like the TOC for instance. In the end, it may reflect on your story in a negative way.
That is where the hand coding comes in. It takes a great deal of patience, attention to detail, and a knowledge of how to create the source code so it is visually pleasing, consistent when reading, and easy to navigate. You must write a great book, but your presentation is as important. So, just as you need a professional editor to make sure the copy is polished, you should have a professional create the files needed for self-publishing your book.