There are 2 ways to upgrade repos: 1. "svnadmin upgrade" 2. "svnadmin dump | svnadmin load" The former will help but will not enable the best features enabled by the newer SVN releases. Only the latter will enable all of the new features. Also, if you're just loading up a new server, I'd suggest you jump up directly to SVN 1.9.4 !
One other thing to note: it's ok to "rsync" (copy) the repository bits from "like to like" in terms of OS-flavor and Bit-ness, but not "like to unlike". So if you're moving from Windows to Linux (or from 32-bit to 64-bit or both) then you should always "svnadmin dump" on the "from" system and "svnadmin load" on the "to" system.