Finding the barcode of my MacBook Air

Hello the room...

I want to sell my MacBook Air Retina 13inch, 2018 serial #FV***K7D but were I want to post it for sale (a local version of eBay called Mercado Libre here in Argentina) ask for the barcode.

They tell me I can get it here in Apple. I don't find de box where the barcode is, I bought it in Miami five years ago at the Apple Store downtown.

To be sincere, I'm at a loss.

I would greatly appreciate any help, directions, suggestion as to where I can get it.

Thank you very much!

Cheers...

Carlos

[Edited by Moderator]