The first 10 ordinal numbers can probably be considered basic knowledge by just about anyone who speaks or is learning Portuguese. The lesson the books don’t teach you is what happens after décimo (10th)? How does one say 11th or even something crazy like 44,999th? I would teach you here if I thought there was a way to teach it aside from employing basic memorization skills. Since that is the case, I recommend seeing the Números Ordinais section of this Wikipedia page.
By the way, 11th is either undécimo or décimo primeiro while 44,999th is a bit Germanesque* in length, quarenta e quatro milésimo noningentésimo nonagésimo nono!
* – I’m refering to das Kompositum.