How to 301 redirect a subdomain to a subfolder?

Can someone point me to a proper coding to use in the htaccess file if I want to redirect a subdomain to a subfolder?

Lets say I need to redirect:

http://testpage.mysite.com

to

http://mysite.com/subdomain/testpage

What rule to use? Also, do I need to delete the directory (folder) of testpage in the cPanel - public_html directory, or can I leave it there (it has its own htaccess file that might interfere).

Thanks.

 

AFAIK, the subdomain is also in the FTP, a folder.
If you have http://example0.domain.com you also have http://domain.com/example0.

By the way, the htaccess code for 301 redirect is:

Redirect 301 /old/ http://domain.com/new/

Code (markup):

 

I am not sure how to write this. I tried:

Didn't work.

 

Try

Redirect 301 http://testpage.mysite.com/ http://mysite.com/testpage/

Code (markup):

 

I think it can be configured via cPanel.
When you create or modify subdomain via cPanel
you'll have option to redirect and to determine rootdir domain.