Modular N means, in part, "This permanent enters the battlefield with N +1/+1 counters on it" (C.R. 702.42a). Torpor Orb affects only certain triggered abilities, but the part just cited is not a triggered ability, since it doesn't start with "when", "at", or "whenever" (C.R. 603.1). (The other part of modular N is a triggered ability, but it doesn't trigger whenever certain permanents enter the battlefield, so Torpor Orb doesn't affect that part [C.R. 702.42a, 603.1].) As a result, a creature with Modular will enter the battlefield with as many +1/+1 counters on it as it otherwise would in the absence of Torpor Orb.
See also this thread.