This is a self reply.
The problem was solved by plesk support.
I can "switch to Webalizer in Domains> example.com> Hosting Settings".
Plesk onyx is wonderful! :)
I searched for logs in the past but I could not find a solution.
I would like to run webalizer on Plesk. Webstat is running now by default.
However, since I use webalizer for a long time, I want to run webalizer.
Is the below a correct tutorial ?
How to recalculate webalizer statistics...