The simplest way is using:

svnadmin dump path/to/repos > repos.out
This will create a portable format for your repository (with history) in the file repos.out. You can then use

svnadmin load path/to/newrepos < repos.out

Ref: http://stackoverflow.com/questions/939963/how-do-i-migrate-an-svn-repository-to-another-svn-repository