title_body: How can I upload my 100+ ebook collection to kindle cloud?
upvoted_answer: If you use the Send to Kindle function, your books may end up stored as Documents. Kindle ownership gives 5 GB Cloud storage, so log into your Cloud Storage first and see how much you are already using (all your Documents back up here). If you want more storage, you have to buy it.
  
  How to do it? I'd use Calibre's own download to disk function to put them on my computer, locate the files and right click to use the Send to Kindle. Yes, 100 books is a lot, but if you want to send big batches of data, I'd check with Amazon Customer service first to see if there is a way to do that. I suspect not unless you submit zip files, since they won't want their system flooded.