MyBB Community Forums

I want a counter of forum views (like how many people has viewed this forum, not a thread or section, the whole forum)

I think I should Edit Template index_stats, but I don't know what code should I put there, any help?

This is not logged by MyBB. You could likely install some stats from some service to display it with JS. Honestly though, site counters are dated and I rarely see them anymore.