Tazkiah (تزكية) is an Arabic-Islamic term alluding to "tazkiyah al-nafs" meaning "sanctification" or "purification of the self". This refers to the process of transforming the nafs (carnal self or desires) from its deplorable state of self-centrality through various spiritual stages towards the level of purity and submission to the Will of Allah.
If you are 100% sure that the chocolate packet touched a part of the floor that definitely became najjs, and that the chocolate packet had moisture on it, then yes it would be najis. This would easy to purify as you could merely put the packet under a tap or just remove the chocolates. If however the floor was dry and so was the packet, then it isn't najis.
May Allah grant you success
I have a tutorial on this, where you are able to see in practice how this is done:
Just wash your hands with water, one time if water is connected to tab or big quantity, and two times if water is in small quantity. Obviously, no Najis material should be on your hands.
There are many books on this subject, but not all of them are translated in English.
One of the well known books which are translated in English is Jami' Al-Sa'adaat by Al-Naraaqi (The Collector of Felicities).
You may also see Mir'aat Al-Rashaad مراة الرشاد by Shaikh Abdullah Al-Mamaqani.