I want to simulate 6N1 and 6H2 teriode in Orcad but Orcad haven't any model for this type of vacuum tube in its library.
How can find and implement this devices or similar devices in Orcad?

 

There are quite a few vacuum tube spice models available on the internet, but I can't find either of those.

 

Try this:
http://tdsl.duncanamps.com/dcigna/tubes/spice/index.html

There seems to be a lot of DIY attitude when it comes to vacuum tubes - more web pages are about creating your own spice models than providing ready-to-use models. For further research, try these:
http://www.normankoren.com/Audio/Tubemodspice_article.html
some of the links at http://www.next-tube.com/links.php