how do i reinstall ios or ipados?

Restoring your iPad to Factory Settings will completely reset the iPad - and install a fresh copy of the most recent version of iOS/iPadOS that is supported by your iPad.

Restore your iPhone, iPad or iPod to factory settings – Apple Support

You’ll need access to either a PC (with iTunes installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of MacOS).

Download and use iTunes for Windows – Apple Support

Update to the latest version of iTunes – Apple Support