“to make changes to your payment information, you need to upgrade your Apple TV to the latest version of tvOS.’”
That message means you can’t update account information with the older software. As you also can’t get current software on that older model, you may need to do any account information changes/confirmation/verification on a different device, e.g. a Mac with iTunes, or iPhone, or appleid.apple.com, or by contacting the support staff. If it is unclear what could be the issue with the payment information, then you will need to contact iTunes Support anyway.