The Arduino IDE that you program the Arduino board with will tell you what COM port the device is connected with. Click the 'Tools' menu, then click 'Serial Port'... or check the bottom-right corner of the IDE, mine says 'Arduino UNO on COM1'.
As for boblight, this discussion says the correct format is '/dev/comX' where X is the number of the COM port the device is connected to.
I use Arduino and serial port stuff on Windows 8.1. FTDI drivers do get weird sometimes and create tons of COM ports. In the past I've had to show hidden devices in Device Manager:
Open RegEdit and browse to:
Make a new String Value with a name of:
"DEVMGR_SHOW_NONPRESENT_DEVICES". Give it a value of "1".
Then open Device Manager and delete all the unused/old FTDI/Arduino COM port entries. This should get the usable COM port number down, sometimes certain programs can use only low COM port numbers (I think less than 10 or 20, but not certain).