For the ownCloud side you will need to upgrade to 8.2.latest and from there to 10.0.x … Thats the first version which can skip major versions for the upgrade with database migrations, etc.
I would go to 8.2 on the old environment, then do a snapshot backup of both database, storage and config.php. Then install newest CentOS with oC10 on a second machine, get the database and storage connected, and do the upgrade in this test system. Semi packages for 7.2 are perfectly fine.