Weatherlink 5.8-> USBxpress mode

I am completely confused, just upgraded from LA CROSSE to VANTAGEPRO2 and trying to resume the WD & WDL.
My weatherlink is USB, it works fine with the Davis 5.80 program (comport defined as USB), what shall I do in the WD Comport number setup (how can I know what Comport number has windows assigned ?) Can someone explain it to me as I got lost with the advices in the forum, is there a simple and step by step solution ?
shall I try it with the 5.7.1 version ? please…
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