Change from individual to pro

That is simply the Selling PLAN you have upgraded from Individual to Professional, and you will have been charged £30 fee.
Professional is not the same as a Business Seller Account.

Do you actually mean you need to change your account type ? - the legal entity - from Individual to BUSINESS, if you are buying items to sell on for profit.
If so, you will need to provide amazon with your UTR which will be sent to you when you register with HMRC as self-employed.