MyBB Community Forums

What I need is to post threads in multiple forums, just like in wordpress.

Anyone know how to do it or have any plugin for it?

I am willing to pay for it.

I'm not sure if this kind of plugin already exists, but you can ask for it here: https://community.mybb.com/forum-190.html

If I remember well there are global announcements that are visibile in each forum, but they are sticked. Idk if it is what you want, but I tried.

MyBB has a copy thread function already. Probably can be used for your purposes and a plugin should hook into that feature if you want something more robust.