How to migrate from ionic 1 to ionic 2

how to migrate from ionic 1 to ionic 2 ?

There is no real migration path as they are fundamentally different.

Here is some information from Ionic:

Is there any plugin in ionic which will migrate our ionic1 code to ionic2 ?

No. It is completely different.

Nope, this is not possible. Read the PDF I linked, what is described in there is the only upgrade path.

Thanks for the info.

Is there anything in ionic 1 which we can re-use in ionic 2 ?

CSS, Assets, general template “structure” maybe.
I really advice you to go through the PDF I linked, it shows this on an example project.