Need help

( Not sure if the flair fits)

First of all, sorry if I say something very stupid. I'm new to photography, editing and anything that has to do with it.

So, a little background.

I was playing an online puzzle (which I'm not going to say the name to avoid spoilers), and there is a level where (according to my theory) I need to count the exact amount of pixels on a small part of an image. But the needed pixels are all the exact same color, so it's very hard to distinguish where one pixel ends and another begins, and the original photo doesn't have a clear separation into pixels.

So, do any of you know an app or an online tool that will clearly show all the pixels of the photo and will make it easier to distinguish exactly where each pixel begins and ends?