Hi I downloaded this hand file from grabcad here: HUMAN HAND - SOLIDWORKS, Other, STEP / IGES - 3D CAD model - GrabCAD

This is a left hand. I would like to have a right hand, so what I attempted to do is create a plane and then mirror the solid body across the plane to create a right hand.

I receive the following message: only merging features may be patterned. If appropriate, make a pattern of bodies instead.

Since this is a solid body file, I'm not sure why it isn't a merged piece, although I did not make the part at all.

Thanks for help in advance!