Hi,
I really doubt it is possible. Virtual appliance (vApp) is a lock-down OS, therefore it does not provide a way to move the 'backup file' off of the vApp, unlike Windows/Linux/Virtual Machine. Usually, if you are running UM on Windows/Linux/Virtual Machine, then it is possible to 'backup' and restore the 'database' to another UM of same type. With vApps, VM/datastore level snapshots are used for backup and restore purpose.
My suggestion would be to:
1) Get the vApp up and running and it will start gathering newer stats.
2) Power-off the Windows-UM, after a month or so, so that you have month-old data collected on the vApp. In case you want to go back to old historical data, you can always power-on and get the old stats, usually a month old data is good enough for analysis and troubleshooting.
Interesting if you look at the documentation for AIUM, there is a provision to - Migrate vApp UM to Linux system. Perhaps, b'cos they both speak linux.
https://docs.netapp.com/ocum-97/index.jsp?topic=%2Fcom.netapp.doc.onc-um-ag%2FGUID-AC9DFDAB-18D2-4D59-93AB-FF32C0421F7A.html
Thanks!