You must be logged in under the exact same username that registered the blog and who is the Admin of the blog and who purchased the upgrade for the blog to access the required setting. If not then you will not be able to access the setting.
Clicking this link should display all your blogs registered under the same username, including the hidden ones: https://dashboard.wordpress.com/wp-admin/index.php?page=my-blogs&show=hidden
If you do not see the blog here http://en.support.wordpress.com/my-blogs/ then
follow this guide > http://en.support.wordpress.com/my-blogs/#my-blogs-dashboard-visibility
If you have lost your log-in information you can visit https://en.wordpress.com/wp-login.php?action=lostpassword
If required click the "Need More Help" link and complete the form for account recovery.
The only accepted methods of payment follow.
WordPress.com uses PayPal as the payment processor, and as such, can only accept payment from countries they support: https://www.paypal.com/worldwide/
In addition to major credit cards Mastercard, VISA, American Express, Discover, and PayPal https://www.paypal.com/worldwide/ WordPress.com can accept echecks and some debit cards.
The debit card must have a VISA or Mastercard symbol on it, and should work just like a credit card when selecting the VISA or Mastercard option on the payment form, even though it's a debit card.
More about echecks here:
WordPress.com also accept Bitcoin for payment of certain upgrades ( bitcoin cannot be used for domain and premium theme purchases) - you can learn more here: http://en.blog.wordpress.com/2012/11/15/pay-another-way-bitcoin/