The Question and Answer section for A Farewell to Arms is a great resource to ask questions, find answers, and discuss the novel.
The lady in the shop says this because a sword wouldn't be of any use, only guns.
“Have you any need for a sword?” she asked. “I have some used swords very cheap.”
“I’m going to the front,” I said.
“Oh yes, then you won’t need a sword,” she...
Did you have a chapter number to go with this question?
Guam is not mentioned anywhere in the text for A Farewell to Arms. The setting of this novel is Italy.