Need help with output form

-I need my variables and strings in my print function to be separated by underscores _. Thanks.

m, d, y=eval(input("Enter the date like so m, d, y: ")) files=eval(input("How many files?: ")) fName=(input("Enter your family name: "))

FROM THIS: print(fName,m,d,y,".txt")

FORM OUTPUT NEEDS TO BE IN: name_month_day_year.txt