What to do? (FIXED)

I've asked this question like 2 times already and both times the solution was the 4th step in https://mcreator.net/install/mac, which was "type brew reinstall libpng" and I've tried it like 10 times, but it doesn't work. Do you know why it happens or what I should do to fix it other than "brew reinstall libpng?" Because that command doesn't exist on my computer.

Jaceks-Mac-mini-452:~ jaceklip$ brew reinstall libpng

-bash: brew: command not found

This is going to be the last time I will ask this question because I'm kinda starting to lose hope for my usage of the program :(

EDIT: I figured out why it didn't work: I didn't have "libpng" installed. I installed it and now it works :D