Log of antivirus

There are many logs of the solution. All ‘detections’ do go to the event log. What are you trying to do? 

They only told me to look for this information about Sophos Antivirus, but I can't find any Antivirus log, I only find examples of the firewall

The following article may explain why you are finding limited information in the log folders for "Sophos Anti-Virus". 
- Sophos Intercept X for Windows: Product architecture changes

The "Sophos File Scanner" component will be used for on-access scanning in the next-gen agent. It uses an ML engine for the decision-making process, so the information you're able to gather from the logs may be limited. 

If you were looking to test the behaviour observed when a detection is raised, I recommend using an eicar file to Test detection features. As SophosUser930 mentioned, this will be recorded in the Windows Event logs. 

The following article may explain why you are finding limited information in the log folders for "Sophos Anti-Virus". 
- Sophos Intercept X for Windows: Product architecture changes

The "Sophos File Scanner" component will be used for on-access scanning in the next-gen agent. It uses an ML engine for the decision-making process, so the information you're able to gather from the logs may be limited. 

If you were looking to test the behaviour observed when a detection is raised, I recommend using an eicar file to Test detection features. As SophosUser930 mentioned, this will be recorded in the Windows Event logs.