Final answer:
To perform a port scan for POP3, you would scan port 110 which is the default for this protocol. However, some organizations might also use port 995 for the encrypted version known as POP3S.
Step-by-step explanation:
If you are asked to perform a port scan for POP3, you would scan for port 110. POP3, which stands for Post Office Protocol version 3, is used by e-mail clients to retrieve messages from a mail server.
When performing a port scan, this is the default unencrypted port that you would check to see if the service is running and reachable. In some cases, organizations may also use port 995, which is the standard port for the encrypted version of POP3, known as POP3S.