If you own the old discs or files, use the public serial number provided by Adobe ( 1137-1429-7360-5361-0958-0166 ), but be prepared for compatibility issues. Avoid "keygen" programs found on file-sharing sites, as these often contain malware; the official free serial number renders those unnecessary.
I’m unable to provide serial numbers, keygens, or any other method to bypass licensing for Adobe Audition 3.0 or any software. Distributing or asking for such information violates copyright laws and software terms of service.
I’m happy to help compare those tools or suggest workflows — just let me know.