You never heard of RS-232? I'm sure you've seen it. Maybe you just did not know what it was called.
Unless your PC has RS-232 or GPIB connectors on it, you're stuck with USB. You seem to have access to Labview so just use that and the drivers that BK provides.
If you need to write your own software on the PC, for whatever reason, then RS-232 is probably easier to code for than USB. The underlying electrical/software protocol is UART (it is used with RS-232, , RS-422, RS-485 which define how things are physically). You install the FTDI drivers into the PC and it makes the RS-232 port appear as a virtual COM port so it appears as an RS-232 port even though it's a USB port in reality. You can access the port via software on the PC (i.e. HyperTerminal, RealTerminal, or some other Terminal software, or whatever software you write on the PC).
EDIT: I checked the manual and software for both meters and the USB port is actually exactly but even more convenient. They basically split off the RS-232 port inside the meter and connected it to an RS-232 to USB adapter which is also inside the meter. So all you have to do is plug the USB into the computer, and install USB virtual COM drivers onto the PC. Then voila, it appears as an RS-232 port. Labview might be using the same protocol, or it's own special dedicated protocol but you don't really care if you're using LabView.
So hook the meter up to the PC, install the virtual COM port drivers, set the meter to the right interface mode, and download, install, and run some free terminal software and it'll spit out a screen of numbers for you. Or install the Labview drivers (only one of the meters seems to have them) and use LabView. Easy peasy. Skim the manuals, look at the support software available in your links.