You'll need to purchase OS 10.7, Lion, from Apple.
By the way, the last version of Lion (before Mountain Lion) was 10.7.4. That you can get for free. And, that version of Safari you have is compatible with OS 10.7.4.
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.