What type of power adapter or voltage converter for travel to Nicaragua?

Nicaragua uses the 2 blade American style plug at 120 volts 60 hz. so the only things you may need are a 3 prong American to 2 prong American adapter(only if any of your stuff has a 3 prong plug). I strongly recommend you take a good surge protector as third world countries have notoriously flaky electrical systems.

Check the devices that you are taking. Most electronic stuff (phone chargers, laptop adapters) is dual voltage these days and just needs a travel adapter plug. Mains powered electric razors tend to be dual voltage as well. High wattage stuff like hair driers (most good hotels have them built into the bathroom) and hair straighteners leave at home. It'll cost you more for a transformer of the correct capacity and in overweight luggage than to buy a new set of straighteners at your destination if they are a must have. Same goes for coffee making machines. Most hotels have tea/coffee making facilities in the room unless you are going into the boondocks of Outer M'Botoland and even those guys probably have them, if not there's probably a Starbucks down the road.