The "funda protectora" itself (empty, no badge) would be a badge holder or badge protector.

<something> badge or <something> tag, where <something> is ID, identification, conference or admission. By the way, the thing that goes around your neck is called a "lanyard". "What do you call this object?" is a better natural question than "How do you call...".

Thanks for your comment, very helpful. I was dubious because I searched on the internet and I found "badge" and "cockade", the second one didn't sound good to me. Thanks again!

As Jeremy says "What do you call these things?" . Interestingly, here, usually called "lanyard" after the cord that holds it, unless you must refer to the contents for some reason. I see by your lanyard that you are presenting at this conference. If you give an example of the sentence you want, you may get better answers. Please let me see your X. Here is your X. I see by your X that .... Your registration card, there, is only a green day pass so, sorry no free lunch for you. So, short answer, lanyard, if refering to the whole thing is enough. Otherwise, by purpose, eg pass, registration pass, registration, visitor tag, id, visitor id.