@zackliu2017 you could try the following snippet utilizing the UsdGeomBoundable class - Universal Scene Description: UsdGeomBoundable Class Reference :
from pxr import UsdGeom
stage = omni.usd.get_context().get_stage()
prim_path = "/World/Geometry/SM_IndustrialPlasticPallet_A01_01"
prim = stage.GetPrimAtPath(prim_path)
primExtent = UsdGeom.Boundable(prim).GetExtentAttr().Get()
does it work on the first scene you screenshotted, though?
in your second example, i noticed your prim path wasn’t set to the actual geom prim, you left it at the reference prim. have you tried it on the geom prim instead?
one more thing to add, the snippet has more to do with USD API and not so much with replicator API, which is probably why you are getting the error in the last section.