To identify Azure, Amazon, and Google storage use in an organization, you need to look at logs that record internet traffic and requests to these services. HTTP Proxy logs are the most appropriate for this purpose as they capture all HTTP and HTTPS requests made from the network. This includes accesses to cloud storage services like Azure, Amazon S3, and Google Cloud Storage. Authentication logs would not provide information about specific storage service usage, DNS logs would only indicate domain lookups, and web server logs focus on requests to the organization's own web servers.