Restart your iPad - Apple Support
More than one Apple Account is not recommended. You should use your original Apple ID on all of your Apple devices. I suggest abandoning the new one or deleting it.
https://www.wikihow.com/Delete-an-Apple-ID
If you choose to continue with the new Apple Account, it needs a payment method. You can add the payment method without going through the AppStore.
This Apple Account has not yet been used with the App Store -
On a Mac;
• Open the System Settings app (in the menu)
• Chose your Apple Account
• Choose Payment & Shipping
• Add a payment method to your account details
On an iOS/iPadOS device;
• Open the Settings app
• Chose your Apple Account
• Choose Payment & Shipping
• Add a payment method to your account details
Alternatively -
On a Mac;
• Open the System Settings app (in the menu)
• Choose your Apple Account
• Choose Media & Purchases
• Choose View Account
• Choose Manage Payments
• Add a payment method to your account details
On an iOS/iPadOS device;
• Open the Settings app
• Choose your Apple Account
• Choose Media & Purchases
• Choose View Account
• Choose Manage Payments
• Add a payment method to your account details
You can find the acceptable payment methods for your country here;
Payment methods that you can use with your Apple Account - Apple Support
M1 Mac mini, macOS 15.1; Watch, series 10 GPS-only, watchOS 11.1; iPhone 16, iOS 18.1; TV 4th Gen, tvOS 18.1; HomePods, audioOS 18.1 and Airport Express w/ Airplay 2