How to lookup What_id to create a task in Zoho CRM?

I'm trying to create a task in Zoho CRM by creating a new module entry. I'm getting an error: "Zoho CRM says 'required field not found'. Check the input for What_Id and try again."

I'm assuming the What_Id is the "Subject" in the create entry task. I had tried using the value of "Email" here, but I still have the error so I'm assuming it's a lookup field. Any suggestions on how to find the id value for the task subject id?