Mr. Trabb is much more interested in Pip once he has money.
It is much easier to use the etext for page numbers. I have included enotes pdf page numbers here.
Pip was a poor blacksmith’s nephew until Magwitch elevated him. Trabb did not expect Pip to have anything to spend money with. He did not come to Pip because he “did not think it worth his while to come” (p. 105). When Pip came to Mr. Trabb in chapter 19, he told him that he had money now.
“Mr. Trabb,” said I, “it's an unpleasant thing to have to mention, because it looks like boasting; but I have come into a handsome property.” (p. 105)
When Pip told him this, a “change passed over Mr. Trabb” and he was suddenly very interested. Now Trabb bows respectfully. Pip and Trabb’s employee, whom Pip calls “Trabb’s boy” do not get along. Pip calls him “the most audacious boy in all that country-side” and does not like him at all.
[My] first decided experience of the stupendous power of money, was, that it had morally laid upon his back, Trabb's boy. (p. 106)
Pip is beginning to realize that money changes everything. With money comes respect. Now that he has money, he will begin to expect respect too.
The local tailor, Mr. Trabb's attitude towards Pip changes as he(P) goes to order fashionable suits for him. This happens because Trabb learns that Pip has become some rich man's protege. Uncle Pumblechook's attitude changes for the same reason. In his case, it becomes so prominent that his attitude towards Pip changes from patronage to humble attention, bordering almost on servility. Dickens uses both of these incidents to show how money works as a great force in a person's life.
As for the page number, it depends on what edition you are using or where it was published from. More or less, it should be after 2-3 pages of the starting of this Chapter.