As we can see most viewed products in admin dashboard.
I want to use same attribute ( its from report ) to sort products on product catalog sort by dropdown (toolbar.phtml)
or is there any better way to do this?
I strongly recommend this extension. It's not that expensive and it works great. I've used it for CE and EE both with success. Other than sorting by most viewed, you have other sorting options: Best sellers, biggest discounts (and others but these are the most useful).
I'm in no way associated with the extension provider. I just used the extension and liked it.