I haven't heard about any recent terrorist attacks in New Caledonia (there was one back in 1988, but that had government members as hostages, as opposed to tourists or other ordinary bystanders). However, this could just be because it has a smaller population than metropolitan France, rather than a lower per capita risk of terrorism.
Reunion Island, a different French overseas territory, had a suspected terrorist wounding two police in April 2017.
The demographics of New Caledonia are somewhat but not greatly different from those of metropolitan France.
Is there information indicating that New Caledonia is safer for tourists with regards to terrorism than metropolitan France?