Dear aspirant,

You get your migration certificate from the same board you appear your intermediate .
You can visit their site to more about the date when they are providing the same.

Thank you.
Best of luck for your journey ahead.

To apply for Migration Certificate, you should send your application along with fee to the Deputy Secretary, Central Board of Secondary Education, Regional Office(the state, where you have studied your 10th class).

You can also go through this official link of CBSE. This will provide you all the reqirements :-

https://www.google.com/url?sa=t&source=web&rct=j&url=http://cbse.nic.in/faq/dupform.pdf&ved=2ahUKEwjUlN_48-_hAhWf8HMBHdtFCA0QFjALegQIAhAB&usg=AOvVaw2mQaPt1PhGq4FVYkIYR0PH

Hope it is helpful!!!