Node number and coordinate changing

Hi, I imported a .vtk file (meshed model created by Segment Mesher) from Slicer to ParaView. I used the extract surface filter and then exported the model as .stl file, but the node number of stl file is not the same as the original model (Slicer output).
For each node with specific coordinates, I read the material property (HU) from Slicer and I want to assign it to the corresponding node of stl file, but it seems that in the surface extraction procedure, the node number and coordinates are changed. How can I prevent the model from node changing?
Thank you in advance for your help.

ParaView is only reading what is present in the .stl file, this is more a Slicer question.