Hi,
We recommend to use the mass actions in this case
Via the menu System > Mass actions, create a new action on the data "product" and in the action part, select "export a csv file".
Then check only the desired checkboxes.
Another solution is to select the action "Display the results" this way it will display a dynamic table. And you can edit the values directly in that table.
Or if you want to update all the prices by the same percentace, you can use the action "update the values" and then:
"price_value" = OPERATION "price.price_value*1.10" to increase by 10%.