I have the same issue.  An earlier thread (from 13 years ago) details how it
can be done, but it doesn't work for me.  Essentially, in Set Options > Build,
you can define a local structure for the page names by selecting User-Defined
structure and then input the way the page name is constructed.  But for some
reason, the rule never takes effect and only the randomized file names get
created.

Here's the thread, and if you ever figure it out, please post so I can get it
to work too.
<https://forum.httrack.com/readmsg/10940/10931/index.html>