The outside of the Pawn Shop looks pretty much intact. The building itself is pretty huge with a giant glass window so that customers can see what they have for sale. It is also in the color purple and has a giant sign that says "Pawn Shop" on it.
The Pawn Shop itself hasn't been fully seen inside but through the window you can see many items in it including a grandfather clock, a taco stand, and even the Krusty Krab. The only known employee is the Appraisal Worker and Pawn Shop Owner.
Role in the episode
The Pawn Shop is seen for the first time when Plankton walks up to it and spots the Krusty Krab inside of it. He then runs home to get his money. The Pawn Shop is seen for the last time when Mr. Krabs buys back the Krusty Krab and drives it back to its place. Plankton comes up seconds later and notices the Krusty Krab is gone. The Appraisal Worker tells him he already sold it but offers a taco stand instead. Plankton is, of course, shocked and upset by this.
The Pawn Shop is the second building in the episode "Hello Bikini Bottom!" that is seen and visited twice. The other is Electronics Outhouse.
The shop is bigger than the Krusty Krab itself, we know that because the whole Krusty Krab stood in there on display.
It is unknown why Plankton would want the Krusty Krab.
It is possible that Mr. Krabs left all his belongings in there including the Krabby Patty secret formula.