My iPad has a SIM slot but I don't see any cellular settings in settings. I don't understand, does it mean it's a wifi only but what's the use of a sim slot. Can some help please. It's iPad 4 iOS 10

Thank you. This indeed is a iPad (4th generation) Wi-Fi + Cellular. A few months ago Apple published an update for these legacy iPad models that required to be updated to in order to continue using cellular data. If an iPad was not updated by the given date, you would have to fully restore the iPad to factory settings in order to use cellular data.

Hello,

Could you please post a photo of the location on your iPad that contains what you are referring to as a sim card slot?

What is your iPad’s exact model number?

Settings > General > About

Have you inserted an active SIM card?

You need to activate the cellular data with your carrier first.

Did you open the SIM tray and check if you have any SIM in there?

Perhaps I should have asked in greater detail, please post a photo of where you see this SIM card slot (its physical location on the iPad).

I also need your iPad’s EXACT model number.

You also need a valid data SIM from your carrier, it's not the same SIM as for iPhone.

Note: Without a valid SIM it will only function as a Wi-Fi only iPad.

See the reply from ckuan above regarding a data SIM.

You're welcome.