What connection should I enter for USB printer? (HPLIP)

I am trying to add a HP LaserJet 1320N printer to CUPS. The printer is connected by USB. in the CUPS web admin interface, I selected HPLIP, then on the next page I have to enter Connection. According to HPLIP documentation for connection by USB: You MUST make a selection from the drop down that appears such as "hp:/usb/hp_deskjet_5600?serial=MY31R1K02179".

However there is no dropdown, only a freeform text entry field. So I made a guess and entered hp:/usb/laserjet, but communication with the printer doesn't work.

What should I enter for Connection?

I am running Debian 3.2 with the Lynx text browser on the command line.