cell A looks like below. I need to add - after the 603 all the way down so it will look like this 603-20001 how can I do this quickly.
A
60320001
60320004
60320009
60320017
60320102
60320105
60320107
60320109
60320204
60320207
60320208
60320209
60320304
60320307
60320308
60320309
60320402
60320405
60320407
60320408