Cinda, if you're still reading this anymore, the answer to your question is if the 8/3 has 3 insulated conductors ( usually black, red, and white) you certainly can use it for a dryer.
Simply install a 2 pole 30 amp breaker, put the black and red on the breaker and the white on the ground/neutral bus. (It's the one with all the other white and bare wires on it).
Install a 30 amp 3 wire 'crowfoot' receptacle. Get a 3 wire dryer cord to match the receptacle. If the dryer already has a 3 wire cord on it, you're done.
If the dryer had a 4 wire cord on it, you'll need to bond the frame of the dryer to the neutral. (it's the center wire of the cord). There's likely a bonding strap near the terminal block. Just connect the loose end of it to the terminal with the center cord wire.
If you need more help, please post again here. There's about a dozen of us here who know how to do this properly.
Rob