Motorola PCI 3 is a chipset. It is used by many different modem manufacturers. The best place to get the correct driver for your specific operating system is the modem manufacturer's web site. If the manufacturer is not obvious from labeling on the modem itself and you are located in the U.S., it may be possible to determine by looking up the FCC ID number typically printed on the modem's circuit board at
FCC OET Equipment Authorization. Alternatively, a generic Google search for "motorola PCI 3" may yield a driver on one of the driver repository sites (update antivirus before downloading).