I presume the car was "jump started with the jumper cables connected the wrong way round". You say the car has no power. Do you mean the car has no electrical power or the car starts but has a loss of engine power? If the car has no electrical power you are lucky in that the car has protected itself from damage and blown a main fuse. If the car starts and runs it may have damaged an electrical component due to the reverse polarity and will need to be investigated by a garage.