can NS convert an SO from units to cartons? for example. user enters 100 units of a product that ships in 10 units/cardon, Pick slip should print 10 cartons for the pick quantity

The cartons would need to be setup in the Units of Measure within the standard units. https://5750528.app.netsuite.com/app/help/helpcenter.nl?fid=chapter_n2211898.html

thanks, we do have that set up and are using it. but as far as i can see if you enter an SO line with say 1000 units, NS does not convert that to cartons automatically

Yeah. You have to select the cartons unit on the line when you create the SO.