I have ordered a Pertronic Electronic Ignition from Just Kampers for my 6Volt Beetle. I started to do some investigating and remember reading somewhere that I also needed a 3ohm coil. I have a new coil but I don't know if it is a 3ohm coil or if I really need one, can anyone help please.

Your new purchase should come with instructions.
It's an easy job to measure your coil for resistance.
You will need an ohmmeter ( or a friend who has one )