It may be complex to find simple answers for simple questions when it comes to Salesforce.
There doesn't seem to be a defined location when we can check exactly if Shield is enabled or not, so we have a few check options that should be able to tell us if it's enabled or not.
Method 1 - Checking Encryption Policy:
Navigate to Setup page in Salesforce.
Search "Encryption Policy" in the search bar & navigate to it.
Alternatively, in the quick find search bar you can look for "Encryption Settings". It should be under Security-> Platform Encryption -> Encryption Settings.
If Shield is enabled, you should get a message "Salesforce Shield is enabled for your organization".
Alternatively, you can see if any of the encryptions are toggled on. If so, Shield is enabled.
Method 2 - Licensing:
Navigate to Setup page in Salesforce.
In the Quick Find box, type "Company Information" and select it from the results.
On the Company Information page, locate the User Licenses section.
Look for entries labeled "Salesforce Shield" or related components such as "Event Monitoring," "Platform Encryption," or "Field Audit Trail.". The presence of these licenses indicates that your organization has subscribed to Salesforce Shield or its individual components.