How do I reset my I-pad

Follow these steps.

Some steps might be “unnecessary” but following them will ensure that your data is fully backed-up beforehand (so that you might restore later).

Following them will also prevent the device from becomming “Activation Locked.”

What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support

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

The root certificate store is a somewhat unusual place from which to start a reset request. Are you having issues with that, or with security in general, or possibly with Activation Lock? A reset would usually cure a corrupt root certificate store, but would not resolve an iPad Activation Lock locked to a different Apple ID, for instance.