I need to know how to "vertically scale" a square on Illustrator, and then do a "Horizontal sheer" for a 3D shape but I have no idea what it means or how to do it, if anyone knows I'd appreciate the help, thanks!
Unless I"m missing something....
You can just use the Bounding Box to make an object taller (vertical scale). Grab a handle and drag vertically. Or, you can input a Height value in the Control Bar or Transform Panel to increase and object's height.
Then you can use the Free Transform tool to skew the shape. Or again, use the Transform Panel to add skew.