Importing blog to wordpress – blog page URLS changed

I’ve just transferred my blog over from a wordpress.com hosted one (with my own domain rather than a .wordpress.com one), to a self hosted one here.

The blog posts and titles have all been transferred sucessfully, but the problem I have is that the links to each blog post have been changed to the extension /?p=NUMBER. So where my old links were EXAMPLE.com/name-of-my-post, they’re now EXAMPLE.com/?p=XX.

Is there any way to change these back to how they were before? Any links that appear to particular blog posts are now broken, so I’m keen to resolve this.