I just need a clearance from expert. I need to translate whole site in other language. My site is consist of the 100 of articles. I need to get that whole article translated. Should I create .po or xml file for each article
If above is only way then let me know efficient way to create .po and xml files as these are not small messages.
I see you've tagged your post with 'expressionengine', so I'm assuming that your site is built on EE. In which case, neither .po files nor XML files are the way to go. Since EE offers completely customizable fields and channels, you can have you secondary language content managed just like your primary language content.
There are many different approaches to this in EE, each with their own pros and cons. This article linked below gives a great overview of the many approaches, and offers many links to additional reading. It's more than one answer on SO can properly cover.
Multi-language Solutions for ExpressionEngine on EE Insider