how can I install the Pro version

The easiest way is to use Rufus and install from a pen drive:

https://rufus.akeo.ie/

You could also burn the ISO file to a disc and install from there, but I've made the experience that the latest Win 10 version 1803 no longer fits on a single DVD - so the remaining option would be to use a BD disc for that (which really would be a waste of money).

I mean the pro version not home cause its says home/pro when I download it 

The ISO file contains both the Home and Pro versions. Depending on the product key you enter, you can install either of these.

22 hours ago, Jan Krohn said:

The easiest way is to use Rufus and install from a pen drive:

https://rufus.akeo.ie/

You could also burn the ISO file to a disc and install from there, but I've made the experience that the latest Win 10 version 1803 no longer fits on a single DVD - so the remaining option would be to use a BD disc for that (which really would be a waste of money).

You've forgotten that DL DVD(+-)R do exist !

But +1 for RUFUS, I'm using it since its inception, it's much better than burning a disc, or even using other USB creation tools.