How can I check my macbook for viruses

There are currently no viruses that affect Macs so that one's easy. For other malware, I would recommend downloading the free version of Malwarebytes. You can run it and then delete it. There is no need to subscribe to the paid version.

https://www.malwarebytes.com/

But, most importantly, carefully read this article:

Effective defenses against malware and ot… - Apple Community