Yup, it does matter what way u plug it in, u will notice the plug has corners missing on one edge correspong with the socket, thus they should only go in one way... if it were put in the wrong way u'd have reversed stereo and a deformed plug/socket.

...and yup your cable should work fine.

But... do u really need those cables? They're an old method of getting sound from an Audio CD to the Sound Card the analog way...

Most CD Drives are capable of DAE (digital audio extraction) so all u need is the right program and those cables are not needed for anything. U'll get better digital quality and save a bit of clutter in the PC case