Question about Zoom H2n

If I understand correctly, they want to record a video and bring in the sound separately with the Zoom H2n.
Answer: Yes, it needs a cable with a 3.5mm jack plug (stereo jack) on both sides. However, it would make more sense to record onto the memory card. Then you can use a suitable video editing programme to merge the picture and sound and add suitable music parts.
The H2n can record directly onto a memory card, be connected to a recording device via a cable with a 3.5mm jack plug or be used directly on a computer via a USB cable.
The H2n cannot accept signals from, for example, a video camera (start-stop).