Could you count the number of the origami paper?
Can you guess how many credit cards Koichi has in his wallet at the moment?
I’m not exactly sure how many stickers I’m going to order yet, but I think it will be at least one hundred.
You have flat objects. You have a number of them. These flat objects are flat things, right? Flat things like sheets of paper, perhaps (or other sheets of things). So, this word is number of sheets.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.