Hi Tigergran,
This was more than likely just a message trying to scare you into think you have a virus. That being said if you would like to check your computer for malware, try a program called Malwarebytes. It is not a free app, but I do believe you can install it and scan your harddrive for known malware without cost. You can move forward with purchasing or not at that point.
The following Apple Support documents may help:
-> Security and your Apple ID - Apple Support
-> Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support
<edit: fixed a typo>