How to make mesh render objects overlay UI?

Good day. I need that objects of mesh render (puzzles) overlay UI when user pick them. I saw similar topic on this forum and made(I think so) all as was recommended in those answer: set render mode as Screen Space Camera and include my puzzle pieces in UI hierarchy.

It didn't help. I still have this:

I also tried to move panel, whose children are puzzle pieces, by Z axis:

 var leftpanel = GameObject.Find("ExampleScenesUICanvas/PuzlePanel/PanelWithPieces/LeftPanel").gameObject;
 leftpanel.GetComponent<RectTransform>().localPosition = new Vector3(leftpanel.GetComponent<RectTransform>().localPosition.x, leftpanel.GetComponent<RectTransform>().localPosition.y, -100.0f);

Doesn't help. If I try to move pieces themselfs they just dissapear into somewhere in unity's universe. Is there any way to manage overlaying without localpostion or position or change Z axis by hands?