I require to move a trailer of 1000 kgs using a electric motor. What is the power of the motor I need to use. (what motor do I need to us)

You need to be more specific as to the conditions you need to be able to handle. Is the surface you are moving the trailer across flat, or do you need to be able to pull the trailer up an incline? At what speed? In theory you could do this with a toy electric motor and a 1-1/2 volt battery if you had the right gear set, the surface is flat, and you don't care how long it takes.