buyer detail by serial number

I am not sure what you are asking for;

1. are you asking for personal details by asking for a serial number?
2. are you wanting a serial number a unit someone is selling on a site like EBay?

I ask this last part because if your suspicious something is stolen good, you can report it to eBay and they will request the information and get the police to trace the serial number against stolen goods lists reported. but you will have to seriously explain yourself to them before they start any investigation