In Unisphere go to System > Statistics for block. Click on Performance Data Logging. Check Periodic Archiving and change Stop Automatically After: to 5 or 7 days, depending on what is a representative sample of your VNX workload.
Click on Start and accept all the warnings. Your screen will look something like this:
After the 5 or 7 days, the customer needs to retrieve the NAR files and upload them to FTP or any other way so you can upload them to MiTrend.
In Unisphere go to System > Monitoring and Alerts > Statistics for Block > Retrieve Archive and get all the .NAR files from last week. We only need data from one SP. If you can also run an transfer an SP Collect that would be helpful too. Once you have all the .NAR files and one .zip (SP Collect) file, create one single .zip or .rar file an upload them to FTP.