About the iPad and SIM-card.

My Grandfathar bought an iPad. We can´t find a way to put in the SIM-card.

It is an A1458. Of course you can plug in a sim card for all iPads? Or am I wrong? It seems like everyone in the store told my Grandfather that it was going to be possible.

I have an iPhone but I´ve never even touch an iPod, how is it possible to use internet without an SIM-card?

Please answer me! ♥