@Butterflyyogi: Have you restarted the device since you created the 'cover' file?
Also, there might be some Finder trickery involved, because I see *two* 'cover' files, which means (at least) one of them HAS an extension.
Provided your Kindle drive appears as 'Kindle', firing up Terminal (hidden away in Applications > Utilities [Or the "Other" group in Launchpad]) and entering
Code:
touch /Volumes/Kindle/linkss/cover
should do the trick.
EDIT: FWIW, in Finder's preferences, the "Show all filename extensions" checkbox in the "Advanced" tab is your friend

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EDIT^2: Unless that's not actually Finder at all, but a Linux file manager trying to look like Finder, in which case, which DE are you running?
EDIT^3: Nope, definitely looks like Finder in three panes view

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