Let's say the prompt is, "What is the store number?" 
The user types in 123 and hits start and what's printed is an IP address in the form of "10.1.23.111" where [10] and [111] are always fixed.
Simple answer - you can't from just entering your 3 digits in your example (i.e: 123) as any octet within an IPv4 address (###.###.###.###) can be a value between 0-255.
However, if you format the User's input to take that into consideration (i.e: 1023) to create 10.1.023.111, that'll be significantly easier.
How would I take a 3 digit number from a Tkinter entry and translate it into an IP address?