I want to know how to update old plugins. Thank you.
It depends on what's not working, what version of MyBB it was originally developed for, and how much programming knowledge you have.
It was made in 2009 and I have 0 Programming knowledge.
What exactly isn't working? Chances are it'll only require a small amount of work.
It depends on the functions of the plugin. Some plugins are simple and don't need anything but a version change, and others require renaming functions or re-doing the entire thing.