we have successfully installed Exchange 2013, and able to connect to ECP.

The Exchange 2010 servers are at sp3.

Issue: We are unable to create public folders in 2013, as it shows "error An existing public folder deployment has been detected.. To migrate existing public folder data, create new public folder mailbox using -HoldForMigration switch.

can you please advise on the instructions on how to migrate all Public folders from 2010 to

Any response to this question yet? Very little online about this issue.  Come on Microsoft, let's not go backwards.  What ever happened to standing on the shoulder of giants?  Exchange 2013 has been out for months and we still don't have an answer to a pretty basic and fundamental question.  Sort it out please :(

Hello Girish Bakshi, Murf_yeha,

There actually is a nice, official documentation on the process, that walks you through it step-by-step:
Migrate Public Folders to Exchange 2013 from Previous Versions

Be advised however, that as Public Folders in 2013 states, public folders at the 2013 level cannot be accessed by legacy-mailboxes. So you may want to make sure your user-mailboxes get transfered first, if you haven't already. Mailboxes on the Exchange 2013 will be able to access a legacy-public-folders-structure while it still exists.

Hope this helped,
Fred