What type of power connector does a floppy disk use?
It varies. There's no universally adopted external floppy disk
drive standard, so it depends on the type of drive and/or computer
you have.
Modern (2008) external floppy drives commonly use USB (Universal
Serial Bus). This isn't really a "floppy drive connector"; it's
just an ordinary USB connector. The drive unit itself contains the
electronics to make the floppy drive work with USB computers.
The original IBM-PC line (circa 1981) included an external
floppy drive option, which used a 37-pin D-shell sub-miniature
connector. These weren't all that common to begin with, and are
extremely rare these days.
The early Macintosh computers (circa 1984) included an external
floppy drive port, which used a 19-pin D-shell sub-miniature
connector.
SCSI floppy disk drives exist, but were always fairly rare.
Some manufacturers introduced external floppy drives with
manufacturers-specific (non-standard) connectors. Generally, you
had to use the manufacturer's expansion card and floppy drive
together.
Some manufacturer external floppy connectors were mechanically
compatible with the 25-pin D-shell sub-miniature parallel port
connector. This allowed the same computer port to be used for
either printer or floppy. However, parallel and floppy are not
electrically compatible, so only a computer specifically designed
for this would work. Dell used it in some of their laptops
(Latitude C series, for example).