I have a question. Does it even make sense to post in this thread about a very old plagiarism? For example, if a user posted plagiarism in 2015-2016. Judging by their previous experience, usually such cases are ignored or the moderators simply delete the posts.
In 2016, I didn't even know this forum existed, but the rule about plagiarism would have only appeared in ~2016 :
If for your case, there is only one case of plagiarism, I would feel like telling you to forget it.
If there are really a lot of plagiarism cases for the same user, you can try to report.
(This is just my opinion)