The Installation and Licensing GUide for upgrading from DP 6.0 to 6.2 can be found at
HPUX 11.11 is a supported OS for DP 6.2, so you should be able to upgrade, which will do the IDB conversion
Once this is done, do a IDB backup to tape. Install DP 7 on the new machine, attach your tape device to it, configure it as a Logical device import the tape. Then, you need to restore the IDB to a temporary directory, stop DP,
cd /var/opt/omni
mv db40 db40.new
cp -R [temporary restore location]/db40 db40
Start DP, it should come up with the restored IDB
I am going to recommend that you download the DP 5.5 Admin Guide
and review Chapter 11, especially where it comes to Backing up and REstoring the IDB