The kanji and the word are almost exactly the same. When you see this word after a number, it’s for physical bills of money.
This is a suffix that takes the on’yomi reading, which you’ve learned already!
You'll also see this pronounced ふだ, but that's when it's a standalone word or part of a compound, rather than a suffix. So if you answer with that reading, you'll be prompted to enter the suffix reading instead.
10000 yen bill
100 dollar bill
1000 yen bill
Can I get the change all in 1,000 yen bills?
Is it okay to use a hundred dollar bill?
I only have 10,000 yen bills.