"I knew about that."
Translation:Mi sciis pri tio.
"Koni" is to be acquainted with someone. (If you know Spanish, it's like "conocer".)
"Scii" is to know a fact, or to know about something. (Like Spanish "saber".)
mizinamo is true. In English there is only 1 word, in other languages there are two. koni = conocor, connaitre, kennen, научиться scii = saber, savoir, wissen, знать