can i check serial number on lin for my macbook pro 2021

do you mean that you don't know your serial number but would like to find it? if that is what you mean, and if you've associated your MBP with your Apple ID, then while you are signed in with your Apple ID, you can use this link > https://mysupport.apple.com/ and you will be shown the serial number for all your apple devices.

Check Your Service and Support Coverage - Apple Support

Why do you want to check the number? Do you think you bought a stolen computer?