sim card

Generally this can be done with a small paperclip, one which is small enough to fit smoothly into the SIM Tray hole.

See Remove or switch the SIM card in your iPhone or iPad – Apple Support for information on removing your iPhone's SIM Card.

Hope this helps!

it's not a key, something thin enough to enter the hole and sturdy enough to apply enough pressure to push out the tray would work.

Use a paper clip.

Open the tray and tilt the device to let it drop out.