Newton is a unit of force. The force applied over a particular distance gives energy. This can be expressed either as Newton meter or in the SI unit which for energy is joule. Watt is the SI unit for power. Power is energy per unit time or Joule/second. It is not possible to convert energy to power directly.
You can calculate power if you know the duration of time over which the energy was converted. For example, if 10 joule of energy is used to heat a room in 5 seconds, the power consumption is 2 watt.
You cannot directly convert Nm or J to W as they are not equivalent units.
To convert energy into power, you can use formula:
Energy= power x time
or you can use this formula:
Power = Energy / time