It's probably too late...
How can we generate or extract the data for 3 months in an hourly basis if this is our setting?
You cannot because hourly statistics are stored 30 days and then averaged as a single value for a day range in the daily statistics.
You will be able to produce hourly statistics for the last 30 days, older than that you lose accuracy.
If you need to produce such reports every quarter, increase the "For hourly statistics will be summarized into daily statistics after XX days" to 90 at least. Note that it will increase your disk space requirements on the DB server.
Where is this setting?
I would completely agree with Yann's advice.Once you have started retaining the hourly data for 90 days this is where you could create a Report for the same.
Open Orion Report Writer-->click New-->select Advanced SQL option from the list and come up with the SQL query satisfying your needs.
To change the Polling settings,log into the GUI and select Settings(top right corner).And then select Polling settings under settings tab on that page.Then you can take control of the settings explained in this thwack.