iPad Air 2 sim slot

To start with, you have to have a wi-fi + Cellular iPad. Not all iPads are cellular capable. See this support document for the location of SIM slots on devices. Remove or switch the SIM card in your iPhone or iPad - Apple Support

If you still experience a problem go to Settings>General>About>Model number and come back here are report that.

I would suggest if you can't find it then you don't have it

It's around one of the edges

Please provide the full model number

Do you have an iPad Air 2 which has a SIM card holder?

That is why I asked you to post your model number to help us determine if you even have a cellular iPad.