The KL was only sold in Europe and had a 3G radio, so that's not what you want. Most likely yours is the TF700T (last one in the left column).
On the next screen you select Android as OS
Then scroll down, 3rd one from the top is the 10.6.1.14.10 version for US SKU. That's the latest firmware for this tablet. It does not matter if you had an earlier firmware version on there. You are doing a manual update which will replace the complete software: bootloader, recovery and ROM.
You cannot do a SKU conversion with stock firmware, meaning if you had WW firmware on there, the recovery will refuse to flash US firmware and vice versa. You cannot do any harm here. If the firmware currently installed is different from the one you try to flash it will just fail.
FAT32 is a file system. microSD cards are typically formatted fat32 out of the box. So if you never re-formatted the card you should be ok.
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