I think what you're looking for is Organization > Summary report.   Select Entire Organization, under NETWORK(S)   then the time frame you want, next to Summary Report, right at the top - then look at the Client stats on the RHS.  You can export to Excel if you wish, top right.  If you need more granular than that, I think you'll need to use the API.     If you don't want all Networks, but still more than one, you will need to add a Tag to all the required ones, and filter by that 
						
					
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