Where in The Great Gatsby are the lines, “He and this Wolfshiem bought up a lot of side-street drug-stores here and in Chicago and sold grain...

In my version of the book, the quote comes on page 143 of 193. The quote comes from Tom during an argument he is having with Gatsby and Daisy when Gatsby is trying to convince Daisy to run away with him. There is a fantastic moment when Tom accuses Gatsby of being a bootlegger but then goes on to claim that there is something else far more serious going on.

Nick describes the way that Gatsby looked. He notes that there is this odd look on Gatsby's face that quickly suggests something awful. He even goes so far as to say that it appears that Gatsby had "killed a man." 

Whatever it implied, it was sufficient to drive Daisy away again and ruin any hope that Gatsby had of her running away with him. Whatever it was that Tom found scared her back into the supposed safety of their world.