the screen of my Kindle broke a while ago and I thought I could just transfer the files of my Kindle device onto my Kindle account. I never bothered really setting up a Kindle account because I inherited my Kindle from my grandpa so I don't know his account login or anything of the sort. I am able to transfer some of the books using "Send to Kindle" that Amazon suggests but some of the book files are unsupported (these books were legitimately purchased very long ago but the files are APNX and not pdf). How can I resolve this? Or is fixing the screen the only way?