[Deskisamess]

On the iOS version 11 the Send To Kindle is a choice in C.C. after you select READ for a book.

Select the book, then select READ at the upper right, two rows of options show up, showing apps you have on the device, Send to Kindle is one of the choices on the top row.

Not having a email account set up on the device will be problematic. You have to have a “sending” email address added to the approved list of senders on Amazon in order to email books to your Kindle.

There is at least one online CONVERT site that I’ve used to convert books, and then send to my devices. I can do it all from my iPad, with no need to use Calibre.