Here you go:
(1) Click on your user name near the upper right corner of the page. This will take you to your Control Panel.
(2) Click [ Find all posts by this member ] - it's a link just above your avatar, on the left. A list of all the posts you've ever made will appear.
Note: If you do not see a post you expect to find, maybe it was deleted. If you attempt to start a new topic in the wrong forum, it may be deleted.