What Cable do I need to use my Zoom H2 mic as an external mic on a Rebel T5i?

The cable that has one end to fit correctly to the mic and the other end to fit precisely to the camera's mic port. Bring mic and camera to the store to be sure you get the right one.

im not sure you can use it that way. the h2 only has either usb operation (as a usb pc external digital audio interface)or headphones/line out. whereas the rebel needs a mic in(different sort of input). it might cope as it does have adjustments for levels of mic recording, but i wouldnt bet on it. as far as i can tell the mic in on the rebel is for a condenser mic(non powered mic). you may need to think again. your manual for the rebel is poor and offers no help. the manual for the zoom is much better. there are other audio interfaces specifically for digital camcorders/cameras such as Beachtek dxa which i have one of and works well and can be bought on ebay for about 20-30 dollars/pounds which allows fitting of xlr style pro mics and may work with the h2 output but best to check with them.

As long as the T5i has a 3.5mm line input (it may be a mic input that can accept a line level input) you will be ok. Just connect the 3.5mm headphone output from the Zoom to the 3.5mm input on the camera using a standard 3.5mm male to male cable:

https://www.amazon.com/Elelink-Stereo-Headphones-i...

If the camera has "mic power" make sure that is turned OFF.

The cable that has one end to fit correctly to the mic and the other end to fit precisely to the camera's mic port. Bring mic and camera to the store to be sure you get the right one.