The default ICONS Assembled doesn't handle the ability to search for a particular mind very well. I'm used to the name "mind scan" from Champions but there's a character named Mind-Scan who instead probes minds. So I've gone with the name "mind search."
If you don't recall, the ability is to sort through all the minds in an area and locate a particular individual. In Great Power, it's probably the power "Super-senses: Telelocation". That power lets you locate a person based on how well you know them.
But it's not a perfect fit for mind search as I've seen it in the comics.
The caveat is that I haven't seen it a lot, so I might have seen a couple of outliers that don't represent the bulk of appearances.
I've seen it used in three applications. The first and probably most obvious is Cerebro. (I predate its big sister.) Cerebro is explicitly said to be doing something telepathic, and in one of the 1960s appearances I saw gave Professor X enough juice to make mental contact. It says "telepathy" on the tin, but I don't think so. Really, it's a human mutant finder. They used it to locate a missing member of the team, probably on more than one occasion, and it needs to be operated by someone with psychic potential. The thing that makes it most psychic to me is that Magneto can hide from it by using certain psychic abilities.
I'd probably go with Detection, except it has this huge range. It's global, and therefore probably a plot device. Even though it started off as the size of Professor Xavier's desk, now it's a big immovable room thing. So I'd probably call it a plot device...but my point is that it finds people who are totally unknown to the user. (That's its purpose.) Telelocation talks about how well you know them.
Yeah, you can get around that, but still...
The second case was in Teen Titans. A psychic teenager is enlisted (the details are vague for me; sorry, it's been decades) to find a missing team member. (Heck, for all I know, Steve Dayton has tried this too, in his Menton persona.) Here at least the psychic teenager knew the missing person, so that sort of fits.
The third case is J'onn J'ones, the Martian Manhunter. There's a case in the comics (and in an episode of JLU) where he scans for a particular person, who they've just met. The impression I get from JLU is that he's opening minds and peeking inside. (Well, opening the doors of his mind and searching through the stuff that washes in.)
You can make the case that he failed because he didn't know the person well, but it didn't seem like that. It seemed, in ICONS terms, like there was a side-effect, maybe mental blast, that scaled according to how many minds he looked at.
I don't really have a good answer. Mind-search is a rare power anyway, and it's a plot destroyer in many ways....I think that's why Steve Kenson put the "how well you know" limitation on it. It's probably best done as a stunt, anyway, probably with the Telelocation sense. I might not make it how well you know the person; I might make it how many minds are in the area being searched. (Maybe the Champions influence. That always seemed game-able to me, though the scale wasn't useful.) The person's mind (and possible Mental Resistance) are the opposition, and the number of minds in the area is some kind of modifier. Any character limits on range are in effect.
The number of degrees of success tell you how well you locate the person: Marginal success establishes only that they're alive, Moderate success pinpoints the city, Major or better success gives you an area roughly the size of a block. With Moderate success, you can try some kind of mental contact, which may of course be opposed.
(Edited to name the Steves.)