Take a bulb out and check the data stamped on the base.
If you have a new(ish) caravan, then the bulbs should be 12V 10Watt Halogen bulbs already.
If they aren't, and the caravan and fittings are old, then there is the risk of damaging the bulb holders because the Halogen bulbs run a lot hotter than "old" Tungsten bulbs.
You may want to think of fitting an additional or replacement 12V spot lamp for those critical areas. These are not expensive, but you'll need to apply a few DIY skills fitting and wiring them into the 12V circuit.
Robert