The PLM-USB/Lan will come automatically with the upgrade Kit or will be build in on an new ProfiLux3. It is a essential part of PL3. The plastics on the backside of the PL3 will cover the first module and has only spaces for this PLM-USB/Lan. The electronic part of PLM-USB/Lan will be nearly the same like the PLM-USB but the Lan part is new.
Sure you can use your adapter also but you will get the USB direct on PL3.