I've read FAQ's here
http://manual.calibre-ebook.com/faq.html and even understood some of it, although most isn't relevant to me.
I have no idea how to covert anything, let alone AZW3 (which I have never heard of). I had no idea converting ebooks could be in any way unsafe
I really have tried searching and reading and I'm stuck, so any help will be gratefully received.