from tkinter import *

window = Tk()

def km_to_miles():
    print(e1_value.get())
    miles = float(e1_value.get())*1.6
    t1.insert(END.miles)


b1=Button(window, text='Execute',command=km_to_miles)
b1.grid(row=2, column=3)

e1_value = StringVar()
e1 = Entry(window, textvariable=e1_value)
e1.grid(row=2, column=4)

t1 = Text(window, height=1, width=20)
t1.grid(row=2, column=5)

window.mainloop()