I want to recreate this pixel effect on an image in Photoshop. How can I do that?
It's a kind of posterization effect, where the different graylevels are created with line-grids (brighter > thicker lines).
The crucial part is to find a photo with good contrasts and shadows, that will look good after posterization (eg 3-4 levels in grayscale). A flat lighting will not produce good results.
In PS you can test posterization via
Image > Adjustments > Posterize. If the results looks good, you can redraw the different gray-level zones with the line grids. In your example the artist has very likely added some extra level of styling eg. to the hair.
A similar posterization procedure can be found in this GDSE thread.