I am unable to login to app store using my ipad

See >>> If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support

If u have a vpn disable it

check if terms and conditions are available on settings -name----u should see term and conditions accept it

check if u have a profile activated on settings-general and delete it

access with iPad on iTunes Store if its the first time accessing with this Apple ID on an iPhone or iPad