'Saving a txt file containing comma separated values as .csv file in numbers on Mac

I have a raw data in following format in Atom;

DateofDeath,Name,Age,PlaceofDeath,Decision,yearOfDeath,gender,fractionalDeathYear,ageBracket,gender2
17-Mar-75,Eva Lyons,70,Own home,Unlawful killing,1975,0,1974.71,70-74,Women
07-Aug-78,Sarah Hannah Marsland,86,Own home,Unlawful killing,1978,0,1978.1,85-89,Women
30-Aug-78,Mary Ellen Jordan,73,Own home,Unlawful killing,1978,0,1978.16,70-74,Women
07-Dec-78,Harold Bramwell,73,Own home,Unlawful killing,1978,1,1978.44,70-74,Men

As you can see it is comma separated fields. but I want to save it a .csv in Numbers on Mac. If I just copy and paste I am getting all contents in one column. Can I please get some help here?

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