Go to the totals sheet, and click a cell that contains a formula. That "activates" the formula. Now display the source file, and click the cell that contains the data you're tracking in the Totals tab. The formula in the Totals cell you activated now shows the file name and cell location of the data source. When you click Enter, the cell with the formula displays the data from the other file. Like I said, you'll have to tweak it somewhat. Maintain your formala syntax, but take note of the "address" of the second file and cell location, and use that.

Try a simple test, and just create a SUM formula in any cell, then open another spreadsheet and click a cell that contains a number. Your first spreadsheet displays the content of the cell in the second worksheet. When both spreadsheets are open at the same time, the formula dynamically captures any changes you make to the source data in the second worksheet.

I wouldn't copy because you're copying a formula that is looking for data from another worksheet or tab. The formulas can't find the worksheet they're looking for because they're now in a different place. Instead, make the formula in the first file look for the data in the file where that data lives - in the second file.