Hi,
Welcome to A.Org!
In order to get audio into an Amiga, you'll need a separate sound sampler, which will usually plug into the parallel port.
However, an A600 is going to be way too underpowered to do audio restoration if you mean recording stuff in from tapes/records and cleaning it up... The A600 has too little RAM and not enough processor grunt to do this with any quality.
Don't give up on the A600 entirely though - there are some great Amiga games that'll run just fine on it...
- Ali
