How to combine multiple sheets with large volume of data


I have a large data set (9K rows + 250 columns) so it is broken up into multiple worksheets. Is there a way to combine? I have figured out how to build reports on multiple sheets, but not how to compile the results for a dashboard (ex: count how many records are across all sheets and have this on dashboard with a breakdown of race/gender etc.)

Any thoughts on the best way to approach this?