You can include a link to an old thread if you like- if you feel it's relevant to your topic- I see nothing wrong with that (especially if it saves you from repeating related content)- but it's optional.
Usually it's best to just start a new thread, & as I said, we're trying to get away from razzing those who post on old threads, but it's bound to raise a few smirks when a new member answers a question posed years ago & the one who asked is long-gone.![]()