I don't see a Sim ejection hole on my Ipad 6 gen?

If you have a WiFi Only model of iPad, without Cellular capabilities, your iPad will not have a SIM slot.

The sim tray on your iPad (6th generation), should be on the right side, near the bottom. Please note, this is not the case if you have a WiFi only iPad as this will not have a sim slot.

Remove or switch the SIM card in your iPad – Apple Support (UK)

Not sure which iPad you have? Identify your iPad model.