Cannot connect to app store

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

Try restarting your WiFi Router - as this may be unexpectedly blocking access to some internet resources.

To restart you home router, disconnect power - then wait at least 30 seconds before restarting. When you router has rebooted (which may take several minutes), force-restart your iPad as before.

You might also try changing your iPad DNS settings (set for each WiFi network) from Automatic to Manual - and use a reliable Recursive DNS Service. For recommended DNS servers (configured at your home router and/or your iPad), you might choose one of the following Recursive DNS Providers (IPv4 and IPv6 addresses included below):

Quad9

9.9.9.9

149.112.112.112

2620:fe::fe

2620:fe::9

OpenDNS

208.67.222.222

208.67.220.220

2620:0:ccc::2

2620:0:ccd::2

Cloudflare+APNIC

1.1.1.1

1.0.0.1

2606:4700:4700::1111

2606:4700:4700::1001

Should it be necessary to escalate your issue to Apple Support, the quickest route to engaging with Apple Support will be via the  Get Support link at top-right of this page.