Judging by what you have told us, you have either damaged the floppy drive while you were cleaning it, or you have plugged the ribbon cable incorectly. Make sure the notch at the top of the cable points upwards, and make sure you have it correctly in the motherboard and nothing is loose.
Don't worry too much about floppies, you can always pick up a new drive for 10$ if you have to. Personally I'd just not get a floppy drive, floppys are next to useless nowdays.
power cables are the ones that connect to the power supply unit, there are 4 wires connected to each of the power plugs and you have many in your computer, its impossible to put them in the wrong way so I'm sure you dont have to worry about that.