Answer:
443
Step-by-step explanation:
Cyber security can be defined as preventive practice of protecting computers, software programs, electronic devices, networks, servers and data from potential theft, attack, damage, or unauthorized access by using a body of technology, frameworks, processes and network engineers.
In order to be able to perform secure credit card transactions on your system, you should enable HTTPS operating on port 443.
HTTPS is acronym for Hypertext Transfer Protocol Secure while SSL is acronym for Secure Sockets Layer (SSL). It is a standard protocol designed to enable users securely transport web pages over a transmission control protocol and internet protocol (TCP/IP) network.
Hence, the port that needs to be enabled to allow secure transactions is port 443.