You cannot do this using only a FDD connection. A multi-card reader connects internally to a USB header on your motherboard. Some multi-card readers also have floppy disk drives in them, in which case they would connect to the FDD header on your motherboard (for the FDD part) and the USB header (for the USB/multi-card reader part).
As far as using a FDD connector for a multi-card reader though, this is not possible. Check your motherboard to see if it has an extra USB header. If not you could either purchase an internal USB card (would go in a PCI slot) or an external USB hub, both of which would expand the number of USB ports available to you.