As Quinn continued her story, it actually made sense that the Garcia Family was the one who handled the "op" before—in regards to which Family was involved with Pops—because not only did they deal in organs and copious amounts of narcotics, but they also deal actual people because Jonathan's "daughter", Allie, and the card she handed over to me were a few examples.
However, since their dealings were allegedly "cut off", as Quinn stated, years before we discovered Pops little basement, the people they were dealing with right now must've been the next destination Tracy, Malachi, and his crew went next.
I haven't talked to them in a good while but I just hope that that didn't mean they actually failed.