If the thread has more than one page, then you can look down after the last post and on the right hand side of the page you will see this...

From there you can click on the next page or go to the last page.

Now if you just want to go directly to the last unread post in that topic, then if you look at the top of the page on the first post you'll see view first unread.

Just click on that.

__________________