There are eight monkeys in all. You'll need 4 to help you get to the baboon which you'll fight for posession of the Gale Boomerang, and you'll need all eight to get to the Boss.
Telling you where all of them are would take a lot of time; just check every door & check every chamber thoroughly. I will give you the 4th one though, 'cause you'll need the boomerang to proceed any further. In the room where you had to kill the weird plants by force-feeding them bomb plants, there's an ivy wall with a gap at the bottom. kill the skulltulas on the ivy, jump across and climb, and go through the door. Kill the plants to get the key (use the bomb plant again) and use the key to free the 4th monkey from the cell on the other side of the room.
"I'm cold and there are wolves after me".