What iems do the pigs with the humans?

I think you might be referring to chapter 6. Napoleon begins trading hay, wheat, and eggs with the human neighbors.

it is on charper 9

only

Okay, check out this quote:

The farm had had a fairly successful year, but was still short of money.
There were the bricks, sand, and lime for the schoolroom to be purchased,
and it would also be necessary to begin saving up again for the machinery
for the windmill. Then there were lamp oil and candles for the house. ch 9