App Store no use please help me

Try first to optimize the range of the mobile network, see this Apple article: If you see No Service, Searching, or SOS on your iPhone or iPad -> If you see No Service, Searching, or SOS on your iPhone or iPad - Apple Support

Low Power Mode is On.

Charge the iPhone & wait until the battery is fully charged (100%).

The Low Power Mode will turned off automatically.

You need to have a good Service & Wi-Fi.

If they are On, turn Off Hotspot & VPN.

Charge the battery > 70%.

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

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

-> If you tried all of the above steps and you still can’t connect, contact Apple Support.