Why is my kindle not showing the books?

I have added books to my kindle using usbport. I was reading these books some months ago and now te books not visible on kindle although i can see them when i connect my kindle to my laptop

crwdns2934089:0crwdne2934089:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2889612:0crwdne2889612:0 1
crwdns2934285:0crwdne2934285:0