Mesh not mirroring correctly I'm new to blender and am running into issues with mirroring.  I am trying to mirror the truck's cabin over the z axis but it's mirroring over on the other side of the vehicle. I tried flipping it and moving the origin.  How do i fix this?
First apply rotation using ctrl + a then move your 3d cursor to right edge of the cabin and set the cabin's origin as the 3d cursor(object -> set origin -> origin to 3d cursor).Also move up your boolean modifier above the mirror modifier.