Try it this way:

 

 

I'm trying to connect a particular emitter point to the position of a 3d null layer. I normally use the expression Dan Ebberts and other people have written:
x = thisComp.layer("target");
x.toWorld(x.anchorPoint)
..but since the z position is split out in particular, I don't know how to connect it.

I tried:
x = thisComp.layer("target").transform.position[2];
x.toWorld(x.anchorPoint)
..but AE gives me an error. Anyone know how to write this?>

thanks