Hi @sabra.tarek ,
You can iterate all tags in a linked model and get it's TaggedElementId.
I don't know if it's possible to get the LinkedElementId of a Tagged nested link, as that link doesn't exist in the host document, could be it won't report the linkedElementid?
You would almost have the link itself openend as a model, and then re-create the tags, from reading from the other opened document (with the link that's tagged), in the same Revit session of course.
But you should then be tagging that nested link...or what does need to be tagged.
So you have this structure.
HostModel A
-> LinkeModel B (with tags to C)
-> NestedModel C (linked as overlay or attachement in B?)
Is NestedModel C also directly linked into A?
Ps. For what kind (category) do the tags need to be copied over?