pop up plug in or lightbox plug in

I am looking for a plug in that will come up when someone first visits my website for having to click a box to verify if over 18. I don’t know what this is called just a “pop up” plug in or a “lightbox” plug in. I have found these two but don’t know if that is what I am looking for “pluginbear pop up” or “displet pop” Does anyone know of such a plug in that will do this or what I should I be searching for? Thank you.