i want to do interenship the advocate give any salary

This depends on the respective Advocates. There are some who pay fixed stipend to interns, while many usually don't. However, if you want to get a paid internship, it is better to clarify with the concerned Advocate before joining.

You select some lawyers and contact them.  It completely depends on the advocate to whom you consult.  If you wish to learn work, don't think about salary and the advocate at where you join satisfies with your work, he may give.

Generally no salary is paid to interns.

However, try your luck.

See basically internships are industrial trainings through which a student learns a lot about his/her field as well as explores the real life world and the working conditions he/she will be working in.
Once you join someone as an intern it's obvious that you may not be getting paid for the work as you're not even aware of the basics about the field yet. However, conveyance amount can be provided to you from the first internship but it depends upon the senior/practitioner you're working for.

One thing that's clear is that once you've attained a good amount of knowledge, it's obvious enough that you'll be paid for the work (i.e. internship). But it's not a salary that you'll be paid, amount recived by an intern during his/her internship tenure is known as Stipend, and it's not basically a salary.
Therefore, what you recieve as stipend during your internship depends upon your experience or the specifications that have been listed in the internship advertisement. Thus, acknowledge the difference between both internships and jobs, salaries and stipends.

I'll personally suggest you that currently don't look out for stipend but for Knowledge, keep yourself upto date with all the new laws or provisions introduced and learn about your field as much as you can, because in terms of success Stipend is something that's secondary, while Knowledge & Experience is primary.

Hope you're clear about the concept.

Regards
Kevin M. Paul