Starting with your core issue, if WiFi is not available, start by resetting your network settings:
Settings > General > Reset > Reset Network Settings
If you wish to completely reset your iPad to factory settings, you will need access to either a PC (with iTunes installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of macOS):
Restore your iPhone, iPad or iPod to factory settings – Apple Support
Restoring to Factory Settings will completely erase the iPad - and reinstall a fresh copy of the most recent version of iPadOS supported by your iPad.