If you’re writing a story, you want to make it believable. Do NOT have the person use an axe. That is WAY too much work, and far too time-consuming. Let them use a chain saw to fell the tree and to cut it into fireplace lengths, like 17″. Then they would use a maul and outdoor ideas wedges to split the logs into firewood sized pieces.
A cord is 4′ by 4′ by 8′, which is 128 cubic feet. And it is to be tightly stacked, meaning a chipmunk can get through, but probably not home improvement a squirrel, and certainly not a cat.
How many trees? Well, that obviously depends on the size of the tree, meaning both length and girth. A really big tree can render a full cord. But it would probably take two “average” trees to get a cord. Whether it’s newly cut or aged does not matter. If it’s a full cord of technology wood when you cut, split, and stack it, it beautiful gardens will still be a cord a year later, after it has seasoned.
And don’t forget to have them save the twigs for kindling.
And see if you can work in this saying: “Firewood warms you twice – once when you split DIY Safety it, and once when you burn it.”
Good luck with your story.