If you have the motherboard manual, or can download it, you should find documentation of the front panel pin layouts.
The leads on a case are usually labeled.
Before you move anything, I suggest you take some pictures of what is connected to where.
When you remove the front power leads from the old case, make a note of what they are, where they came from, and where they go.
The pwr and reset switches are momentary contact switched, so polarity(+ -) does not matter.
Tye led switches are polarized, and if you get them reversed, the led will not work, so just reverse them, no harm will be done.