what is a Vat number? where can I find it?

A VAT number is a value-added tax identification number that allows governments to track the VAT activity of registered businesses. These activities include VAT paid, tax credits earned, and VAT taxes charged and collected from customers. (https://quaderno.io/blog/how-to-get-vat-number-business-in-europe/)

I have no idea why Apple (did you mean Adobe?) would ask for one, but you'd probably better ask them. If you meant Adobe, you'll need to contact Customer Care and ask for help as this is a public forum, not Adobe support. Users, including the ACPs and MVPs, can't provide support for account, subscription, billing, download, or product activation issues. Support for those issues requires an Adobe employee.

Click the following to contact Adobe customer support staff for help: 

https://helpx.adobe.com/contact/support.html

You must be signed in with your Adobe ID and allow cookies in your web browser for this to work.

Click the chat icon at the bottom right of the page to open a chat session. Typing AGENT into the chat window should connect you directly to a CSR rather than the AI.

If the CSR refers you to the forums, insist on speaking with a supervisor and keep moving up the chain until you get someone who knows what they are talking about.