Upgrading from crackedcopy to legit LR cc

Hi, I'd like to subscribe to the creative cloud lightroom package. Whilst looking into it online, I noticed many had difficulty to upgrade to LR cc if there current copy was a cracked version. As my computer was bought second hand, I thought i'd run a check and I can see in a folder that there is a cracked code for LR on my drive, so I'm assuming the copy that came on the machine was an illegal, even though it had always updated.

So how to I go about rectifying this and make sure the legit serial number that will come with subscription CC Lr actually gets used and rids me of the old one, and gives me the up to date LR cc.

Thanks in anticipation, Martin