How to apply point value on local coordinate system rather than world coordinate system

Hi all,
I am a beginner at Unity and I have a problem that I ve been struggling with for days.
Through Websockets I get xy coordinates for certain positions. Now I have an object in my Unity scene which is like an anchor or reference point and has another coordinate system than the main camera (e.g. the x axe of the anchors coordinate system is pointing to the right whereas in the main cameras coordinate system x points forward) and would like to first instantiate an object (gameobject like a robot) at the received position and then move this object according to further received positions, most importantly with respect to the anchors coordinate system (which has another coordinate system than the main camera). So e.g. if i get the position (x,y)=(2,0), I would like to first instantiate the object at (2,0) with respect to the coordinate system of the anchor and then if I get (3,0) move it forward. It works when I child a object to another, but since the anchor is already a child of another object and if I child my robot to my anchor somehow its not working and gives me wrong positions when i run. I also tried to use anchor.transform.InversetransformPoint(receivedPositon) but this somehow also dont work. I hope for some replies and thanks in advance!

Instantiate new objects as children to your anchor, and set their position using Transform.localPosition instead of Transfor.position