This should help :
Have a derived col. Have three cols in there as (assume F1 is your excel col):
First_name
expression :SUBSTRING((REPLACE(F1,","," ")),1,FINDSTRING(F1," ",1))
Last_name
expression :
SUBSTRING(F1,FINDSTRING(F1," ",1) + 1,FINDSTRING(F1 + " "," ",2) - FINDSTRING(F1," ",1) - 1)
middle_name
expression :
(FINDSTRING(F1," ",2) > 0) ? REPLACE(SUBSTRING(F1,FINDSTRING(F1," ",2) + 1,FINDSTRING(F1 + " "," ",3) - FINDSTRING(F1," ",2) - 1),".","") : " "
Please let me know if this worked or not