I'm better with Macs, so let's look there first. In the Apple Menu, select 'About This Mac…'. In the 'About' window, click on 'More Info…'
You'll get a different 'About' window. In this one, click on 'System Report…'
In the next window, look in the left-hand pane for the item 'Hardware', and expand it by clicking on the triangle. Underneath 'Hardware', you'll see a list of devices. Select 'USB'. A list of USB devices will appear in the top right pane of the window. Look in there to see if your serial converter appears. If you're not sure, unplug the converter, select 'Refresh Information' from the File menu, and see if the list changes. You can re-connect the converter and note which device ( if any ) has been added back into the list.