Fediverse works strictly by follow relationships. Therefore, if nobody on your instance followed your threads account before now, you won't see any posts, unfortunately.🤷‍♂️😬

However, if you've posted there *after* turning Fediverse on. You can "pull" the post to your instance by clicking the little paper plane on the threads post and copying the link, then paste that link into your mastodon search bar.👍