64k means exactly that, 65536 of allocation size. Sorry for the confusion.
If you didn't yet format it to MBR, then this is the program of choice to format to MBR:
http://www.easeus.com/partition-manager/epm-free.html
The steps are this:
1) Delete all existing partitions using EaseUS Partition Master.
2) Create an MBR partition using EaseUS Partition Master, and select "primary" for the MBR type.
3) Use guiformat to format that partition as FAT32 using 65,536 Allocation unit size.
Be careful to select ONLY your external 3TB drive, of course...