change URIs of migrated site

Site works with “plain” permalinks.

1. Check write permission in your main wordpress dir, maybe wordpress can’t write .htaccess file (you can upload it via FTP).
2. Check if mod_rewrite on server is enabled.

mod_rewrite status can be checked printing phpinfo().
If .htaccess file is missing, upload a similar one:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /tests/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /tests/index.php [L]
</IfModule>

# END WordPress

I used /tests/ in above code, because you wrote

Requested URL http://mysite-site3.itempurl.com:80/tests/
Physical Path h:\root\home\mysite\www\site3\tests\

Maybe you’ll have to change the path /test/.