how do I create formula in excel

If your data is true date time value then use the following formula to separate date-

=INT(A2)

And this is to separate time-

=MOD(A2,1)

If your data is just string then could try [Date]-

=--TEXTBEFORE(A2,",")

[Time]

=--TEXTAFTER(A2,", ")

You must format resulting cells as proper date time formatting. See the attached file.