Convert World and LocalPositions of different objects

In order for a lean ADS i want to move the weapon IK Target relative to the camera. Unfortunately caused of other dependencies i am not able to change the hierarchy .

Current State (Only changing Rotation no camera transition):

At the end i want to Vector3.Lerp the camera left/right → Leaning.

So does anyone know how i can convert the world position of the camera into the local position of the targets coordinate system?

Sry, could upload a picture of the hiearchy somehow.

By using InverseTransformPoint on the transform of your target coordinate system and passing the world space position as parameter.