I'd get one about the same height as ski poles. Hard to say just based on your height. Some people have long legs, etc.

I have adjustable trekking poles that take snow baskets, so I just set them for whatever works at the time. I'm on skis these days, but the principle is the same. I used the same poles when I had snowshoes. I probably set mine so that they are a few inches shorter than shoulder height.

btw, I can't tell from your post, but make sure you buy a pair of them. You can snowshoe without them, but when you need them, you'll probably need both of them, especially if you wear a pack in soft snow.

Eric- after reading your post, I rethought how long I set mine, so edited my answer. I probably set them longer than I first thought.