Do you think the officer is at first surprised to see the stranger at the doorway? Give reason for your answer.

It is very likely that the officer wasn't surprised to see the stranger at the doorway.
The text tells us why. If we refer to Jimmy's letter at the end of the story, we will understand why he may not have been surprised to see Bob (the stranger).
In the letter, Jimmy says that he was at the meeting place on time. Then, he says something very interesting: "I saw the face of the man wanted by Chicago cops." Being a police officer, Jimmy is privy to information about wanted criminals. So, despite the space of twenty years, Jimmy still recognized Bob.
Most importantly, Jimmy and Bob made a pact twenty years ago. So, Jimmy was likely not surprised to see Bob waiting at the doorway of the shop. The text also tells us that Bob wanted to prove he could find success in the West. Once he did, Bob would have returned to New York City to tell Jimmy about it.

I hope Jimmy has done half as well. He was a slow mover. I’ve had to fight for my success. In New York a man doesn’t change much. In the West you learn how to fight for what you get.

So, Jimmy was likely not surprised to see Bob waiting in the doorway of a shop. First, both men made a pact twenty years ago. Second, Jimmy knew that Bob would return to tell him about his success.