I believe your carrier can do that for you, or you can use the desktop software from blackberry to put the contacts into your computer, from there you can sync it with icloud
It has been a long time from my Blackberry days but the maflynn method of using the desktop software to sync with Outlook is what I used and it worked perfectly. That was a long time ago and maybe there is another way.
I have also heard about the Carrier having the equipment to do the same.