The copy-to-stamp tool was deprecated and is no longer available in Houdini 19.5.
The newest way to access the iteration (stamp) attribute would be to create a metadata node in a for-each-point loop and access the iteration attribute.
Connect a for-each-points block to a copy-to-points node
In the foreach_begin1 node hit the create metadata import node button; this will generate the metadata node, which contains the iteration and numiteration detail attributes. We will be accessing these attributes to randomize attributes on the geometry we are copying (stamping)
3. In the geometry node, type "detail("../foreach_begin1_metadata1/", "iteration", 0) . This expression will randomize the radius to differ per point for the sphere. Alternatively, use this expression to vary rotations, color, and noises on geometry to be copied.
Hope this helps!