The files the kindle app uses are already stored on the SD by default look at your sd card via a file explorer you'll find the kindle directory there.... or are you wanting them to go to the actual SD(SDCARD2) card and not the internal memory(SDCARD)... that would be rom dependent.... the only rom I know of that uses the actual SD card as the default storage is CyanogenMod.... all the others, to the best of my knowledge, utilize the internal mem partion as the defualt "SDcard" where app data is stored... If you really want a back up you can copy the kindle directory to the sd card or a pc.. but that's not really necessary.. amazon keeps a backup of all the books you've bought/downloaded... with all my android devices all my books transferd to each of them reguardless of which one i got them on.
And.. if you have e-pub files you want to read on te gtab IMO the best apps to use are aldiko or laputa.. each of these wil allow you to import e-pub , and several other formats, directly into the app from the tablets sd card.
