Need to replicate and mirror precisely

I need to replicate the right blue side to the left, mirrored and precisely oriented. I tried with “insert” but it require me to click and drag, and this completely mess up the position. Any help ?
Thanks a lot as usual!

Maybe try the Gizmo Matrix.
Duplicate the mesh.
In the matrix - uniform scale off - x= -value

Duplicate and flip (symmetry menu)