You can improve on this by using tools such as Topaz Denoise or similar but these will work better with the original sized RAW file. However, you can't get a perfect picture using these techniques you can only get some slight improvements. I've made some quick adjustments as shown below to give you an idea as to what's possible though if you look in the mid-tone areas there is still some noticeable noise. These techniques are always a compromise and it is much much better to get a better photo to start with - ie in better light conditions so you don't have to use such a high ISO setting.
Another, very expensive, alternative is to get a f2.8 lens but that will only allow you to reduce the ISO to around 1200 so the image will still be noisy (though not quite as bad as this one) and you will have spent a few thousand dollars for only a small improvement! Better light is the best option - twilight can be made to look darker by manual exposure control.
