Wifi not showing in control center

Your WiFi and Cellular controls should always be visible in the iPad Control Centre; unlike some other features that can be enabled/disabled from iPad settings, the Control Centre WiFi/BlueTooth/Cellular/Airplane-mode controls cannot be disabled from settings.

If the Control Centre is not operating as expected, perform a forced-restart of your iPad - as this will often resolve an isolated software issue:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button.
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.

have you checked in

settings->control centre

?