You would choose the tube size based on the tire size.

So, for example, if you have a 700c X 35mm tire, then you'd choose a tube that is:

700 x 28/32 or
700 x 35/43

The larger sizes are sometimes harder to install, but have some advantages such as slower leaks. The smaller sizes are often lighter, and potentially easier to install, but the stretching may tend to open up small holes a bit more. However,it is best to be within the ballpark.

Your local department store should have tubes for about $5 each.

The 17c is likely the internal rim width. A bit narrow for a hybrid, but it can still accept a variety of tire sizes.