Cannot run cuda on ubuntu 22.04.1

I am trying to run via termianl a simple program:

include <stdio.h>
__global__ void hello_world_kernel()
    printf("Hello GPU World!\n");

int main()
    hello_world_kernel <<<1,8>>>();

but getting always :
nvcc -o hello_gpu
and it’s outputing always:
./ line 3: syntax error near unexpected token (' ./ line 3: global void hello_world_kernel()’

nvcc --version

nvcc: NVIDIA (R) Cuda compiler driver

Copyright (c) 2005-2021 NVIDIA Corporation

Built on Fri_Dec_17_18:16:03_PST_2021

Cuda compilation tools, release 11.6, V11.6.55

Build cuda_11.6.r11.6/compiler.30794723_0

from nvidia-smi:
NVIDIA-SMI 510.108.03 Driver Version: 510.108.03 CUDA Version: 11.6
I am using conda, I have installed successfully the cuda, because I can run in GPU the tensorflow