missing jpg and opf files after running convert & save

hi,

I'm new to the "import to kindle " world

for some reason, not consistently, when i run a calibri conversion of a EPUB file to be used in kindle, the jpg and opf files go missing.

then , when I try to import the created pdf into kindle , using my ipad, either the book does not import... or it imports as a DOC , usually with no title, rather than a book with pic of the cover and the title of the book showing. any suggestions as to what I'm missing.

Thanks so much for any suggestions