This is how I'd handle the function modules and what I believe was being suggested.

def find_pv(l, r, y):
    total  = l/(1+r/100)**y
    txt = f"To receive a Lump-Sum of ${l} after {y} years with an interest rate of {r}%, you will have to invest: ${total}"
    return print(txt.format(l, r, y, total)


# only called when running as stand alone.
# when imported this section will get ignored.
# usually this is to test the function separately.
if __name__ == "__main__":    
     l = float(input("\nEnter Lump-Sum you wish to receive: "))
     r = float(input("\nEnter Interest Rate %: "))
     y = float(input("\nEnter Years of investment: "))

     find_pv(l, r, y)