I believe you are monitoring cDOT systems. For cDOT systems, you must have also registered NetAppp Storage Virtual Machine (SVM) to the plug-in because storage must be allocated to your database volumes from SVMs. Once you register SVM, you can refer "All Metrics" and click on "Volume Performance" metric. This metric lists the performance details of all the volumes belong to that SVM. Latency has been displayed in terms of micro seconds (ms) in that metric.
Please let us know if it works.
Re: Is there a way to get the Latency of a Specific Volume using NetApp Plugin?