Did you check this link- https://azure.microsoft.com/en-in/blog/monitor-all-azure-backup-protected-workloads-using-log-analytics/#:~:text=You%20can%20open%20the%20diagnostic,%E2%80%9D%20and%20click%20%E2%80%9CSave.%E2%80%9D?
You can also refer to answer here - https://social.msdn.microsoft.com/Forums/en-US/f5701494-1f79-4459-bee7-9d76abc06399/azure-vm-backup-report?forum=windowsazureonlinebackup
Let me know if you need any further help.