All html files are in the folder "htm" in the path: domain.com/htm

How can I make Nginx serve?
domain.com/index.htm
or
domain.com/page.htm

Detail: For SEO reasons, I don't link the url make a 301 redirect or make the site root the folder "htm" (bacause I have some php called by ajax inside the html file, and the php files are all inside the path: domain.com/php).

I tryed:
rewrite /*.htm /htm/$1.htm;

But...
Thanks,
Rogerio.