Edit
includes/functions.class.php
Find and replace
CODE
$forum['moderators_list'] .= '<a href="u' . $moderator['member_id'] . '.html">' . $PowerBB->functions->GetUsernameStyle($moderator['username']) . '</a> | ';
with
CODE
$forum['moderators_list'] .= '<a href="' . $moderator['username'] . '.html">' . $PowerBB->functions->GetUsernameStyle($moderator['username']) . '</a> | ';
find and replace
CODE
return $username = '<a href="u' . $user_id . '.html">' . $username . '</a> ';
with
CODE
return $username = '<a href="' . $StyleMemberInfo['username'] . '.html">' . $username . '</a> ';
Save and upload the file to its place in your forum.
That will change user name link from uXX.html to username.html in most forum pages.
Also there are few templates to modify, I attached these templates in the attached file. just upload and delete forum temp files from the admin cp.