How do I work out my network mask?

Excuse me, could you kindly assist me with a technical query? I'm trying to determine the network mask for my current network setup, but I'm a bit uncertain on the process. Could you explain, in simple terms, how I can calculate or work out the appropriate network mask for my network? I've heard it's crucial for ensuring the smooth functioning of my network and would greatly appreciate your guidance in this matter. Thank you for your time and assistance.