The easiest way is to simply resetup the replication.

If you don’t like that answer…

Backup the publishing database and restore it to the new publisher with the KEEP_REPLICATION flag enabled.

Continue reading Denny Cherry post on below thread:

http://itknowledgeexchange.techtarget.com/itanswers/migrating-sql-server-replication-from-one-server-to-another/