change permalinks to include subdomain

When I start my WordPress site, I set it for the default for permalinks. Example: http://www.mydomain.com/P123

I would like to change the permalinks to make it possible for subdomains and directorys. Example: http://www.mydomain.com/subdomain1/directory1

How can I do this without any manual changing of all the pages as I have a lot of pages.

Thank you for your feedback