Li conosco ==> I know (of) them
what is the action/verb?
(io) conosco = (I) know (of), verb - used to know of people, places, things
who does the action?
(I) = I, subject
what/who does the subject action (what does I know of) ?
Li = them, direct object
Them I know (of) ==> I know (of) them ==> I know them