How to print - stylus 3000 using SERIAL to USB converter

[Carlos Fernando Hernandez]

I got a Stylus 3000 with a serial port and a SERIAL to USB (Keyspan USA28X) converter.

I need to use it under Mac OS X, already installed the gimp and all that stuff but I dont 
know what URI I have to use.

Already try

USB://EPSON/Stylus%20COLOR%203000?serial=0
usb://EPSON/Stylus%20COLOR%203000?serial=P#USA28AX01
file://dev/null

Need some help to know how to verify the connection between the printer and the mac 
and how to set the URI for that connection.

Thanks
Carlos