Others may have seen such a tool and can update this post accordingly, but I'd be surprised if a tool exists. I use both Tasker and MacroDroid, and although they're similar in concept, there are significant differences in details, which I expect would make it hard to create an automated conversion tool.
If your Tasker task is brief enough, and not confidential, you could export/post it and see if someone could give advice on converting it to a MacroDroid macro (or convert it, if it's simple enough).