Allergic to video solutions? The following is for you:
EDIT: PICTURES HAVE BEEN TEMPORARILY TAKEN OFFLINE
EDIT AGAIN: PICTURES ARE BACK
As you progress through Chapter 3, you'll be forced to play through these 'scroll segments' in which the game-play will be moved from 3D to 2D. There are a total of three scroll segments, but only collecting the peaches on the last segment is required. There are 4 peaches to get. [Obviously if you've missed your chance to get them, you can reload the Chapter from Chapter select after it is completed.]
The first peach is immediately after you push a boulder into a series of grasshoppers. You should even be able to see the peach when the boulder cut-scene passes it. Descend after the boulder and you should spot it near a moving platform.
As you progress a little further, and start making your way back up, you'll notice two platforms next to each other. You should be able to spot the 2nd peach, but it won't allow you to grab it.
No worries, just continue as you normally would. You'll just need to go up and around. Fall after the leaf path, and then go left, hopping your way toward the peach.
Progress a ways through the level - you'll stand on couple moving platforms that you'll be forced to shrink and jump to avoid spikes. You'll come across a springing platform that will help you onto a platform that is moving in a circle. After boarding the platform, look left - yonder!
The last one is, like the others - pretty easy to find. When you come across one of those samurai huts in the background, fall left instead of progressing right. Trust the teeth-path and fall onto the ground below.
The chievo will unlock immediately after getting the last peach.