where can I find an antivirus for MacBook Macintosh HD

Your MacBook doesn't require any anti virus product.

Please see

How does Mac OS X protect me?

<http://www.thesafemac.com/mmg-builtin/>

We see far more system panic and performance problems from anti-virus, Mac cleaners, and memory cleaner packages they any other single source.

"Just say No".

mare_ros wrote:

How can I know if my McBook has a virus?

If you are experiencing problems with your Mac, describe the symptoms. Do not seek an "anti-virus" solution for whatever anomaly you may be experiencing.

Where can I find an antivirus for MacBOOK model 7.1

Read Effective defenses against malware and other threats.