Alien registration card for visitors in seoul?

I am from Argentina and I will be on vacation in Seoul for 1 month. I need to apply for a visa for visiting China (I want to visit China after Seoul). I will apply for it while I stay in Seoul. Do I need an alien registration card? It says they give that card to people living in S.Korea for more than 91 days, and I will only be less than 1 month. So how can I get the card to apply to the Chinese entry permit?