How to convert millisecond time stamp to normal date in Python?

You need python's datetime package to do that:

import datetime

date = datetime.datetime.fromtimestamp(milliseconds/1000.0)

date = date.strftime('%Y-%m-%d %H:%M:%S')

you can do this by using to_datetime function https://pandas.pydata.org/docs/reference/api/pandas.to_datetime.html.

df['Millisecond'] = pd.to_datetime(df['Millisecond'], unit='ms')