To know for sure, you need to:
1. Consult a repair manual: A Haynes or Chilton repair manual specific to your 2003 Dodge Durango will list the correct bolt sizes.
2. Check your existing bolts: If you can safely access the bolts, measure the thread diameter and pitch with a thread gauge. This is the most reliable way to know.
3. Check a parts store: Take one of your existing bolts (if accessible) to an auto parts store. They should be able to identify the size.
Do not attempt to guess. Using the wrong size bolt could seriously damage your vehicle.