Where do I see how much I have unpaid

Read this article about how to check your Apple ID balance.—> Check your Apple Account balance - Apple Support

and this one to review your purchase history —> View your purchase history for the App Store, iTunes Store, and other Apple media services - Apple Support

From: How apps, content, and subscriptions from Apple are billed - Apple Support "If none of your payment methods can be charged, your account shows a negative balance. You can't buy more items or update your apps until you update your payment method."

Read this document about how to view your current payment types —> Add a payment method to your Apple ID - Apple Support

If an item appears in red then it is no longer working and you either need to replace it or get it working again by contacting your financial agency (bank).

If you need to replace a payment type, read this article about updating payment methods on various platforms (iPhone, Mac, etc.) —> If you need to change or update your Apple ID payment method - Apple Support

"If you change your address, the credit or debit card information that you use with your Apple ID might be automatically updated by your financial institution, and you don't need to take action. But if there's an issue [such as you having a subscription or being a Family Sharing Organizer], add a new card first, then remove the old card."

Here is how you update your payment method on an iPhone or iPad:

1. Open the Settings app.

2. Tap your name.

3. Tap Payment & Shipping. You might be asked to sign in with your Apple ID.

4. Tap Add Payment Method, enter the new payment method, then tap Done.

5. Tap Edit.

6. Tap the red delete button next to the old payment method, then tap Delete.