Welcome to the forums, newcomer!
Zoom into this image of your motherboard, scroll down to the bottom of the picture's right hand corner, you should be able to see markings of the +ve(positive) and -ve(negative) terminals with which there are pins. You should also be able to see headers from your case's front panel terminating into Dupont connectors with markings of
- or
-ve on said Dupont connectors.
Make and model of your case?