Thanks for asking -
There are lots of ways of searching for donors. You'll see some advice on that on the Power On Network Site.
The "Cheat Sheet" has a list of typical donor searches.
As for your specific request, here's what I understand that you are looking for.
If someone gave any money in the last three years, you would like to get a report showing the total that they gave during that time.
Are you going to make a smart group of the donors?
Will you want to segment the list based on what their total is or do you want to just find anyone who gave money in the last three years?
Here's a way to get the totals - it's not a report, it's a search
Go to Search>Custom Searches
Select Contribution Aggregate
Fill out the form. Attached is an example. Click Search. The result will be a list that you can save as a smart group.
If you want to run a report instead, you could run the "Top Donor Report" for the time period. Or run the SYBUNT report.