You don't need to convert djvu files (in fact, you should NOT because the result is usually 10x bigger, so it is a sheer waste of storage space) in order to view them on Kindle. You just use kpdfdjview available freely here:
https://github.com/tigran123/kindlepdfviewer/downloads
kpdfdjview is a lightweight version of kindlepdfviewer with support for PDF and DjVu. It supports multi-level TOC (aka "outlines" or "bookmarks"), arbitrary page crop, etc.