how to find out the most viewed topics with their no of views?

as i want to reward active user with best quality contents on my forum

Unfortunately, there is not a way to generate this statistic currently via the software. Please leave your suggestion in our official Feature Suggestion forum for further evaluation for a future release.

Keep in mind though views are not the most accurate count of how quality content is. For example:

• A user can view content multiple times and this counts as a view.
• Guest counts can be off due to caching.
• Etc...

It would be worth noting that views are probably not a great statistic for an item being the best quality. It may well be someone just happens to create a topic with a catchy title, or they have linked the item somewhere that gets a lot of traffic. You would be much better to look at reactions for this purpose.