how to lock anchor point for 3d layers

I am not sure what you are trying to do. If you move the anchor point with the Pan Behind tool (y), the position does not change. If you animate the anchor point value, the position will change. The anchor point defines the center of rotation and scale. On shape and text layers, the anchor point default is 0, 0, 0. On all other layers, the anchor point default is half the layer width, half the layer height, and zero. Nulls don't count because they don't render, but the default anchor point for null is also 0, 0, 0.

Your uploaded screenshot (embedding by dragging to the reply field is more efficient) shows a slightly offset position property on a nested comp (pre-comp). Even though the selected layer (Layer 1) does not have collapse transformations turned on, it probably should be on.

It looks like you are creating a box using shape layers. If that is the case, it is not necessary to pre-compose anything. All you have to do is offset the Anchor point in Z to the center of the box and rotate the appropriate layers. Then, you can place a 3D null at the comp center, parent all the surfaces to the 3D Null, and control position and rotation by moving the null. Something like this:

Does that help solve your problem?

or just recentering the anchor point to the middle of the world?