How can I find archived cards for every employee?

[Ross Shemeliak]

I have a column "Weekly done" and "Monthly done" on all boards.

When someone did something during the week, you will move to "weekly done".
So when a new week begins, you move all "done cards" to "monthly done".
After that, when the month ends, you will archive all monthly done cards.

But I want to find or storage all archived tasks for every employee. 
To know what someone did last months or last 3 months. 
It will be helpful for reporting.  

[Carson Buckley]

In the archive you can search @User_name to find anything they were assigned to. If you use labels, you can also search for particular labels.

If there are no direct assignments to individuals, but they have commented on cards, you can search for that as well.