Report of average CPU utilization over time

I want to create a report that shows an overview about the average CPU utilization and memory usage in percent about the last month of different ESXi servers. How to get started here?
Thanks in advance!

You can use the column “Service: Metric History” for that.

That was a good first hint!
Seems to work for “CPU utilization” but for “Memory used” is does not show up anything. What is a requirement for this to work?