|I'm not sure how the mention of the empty cells is relevant here. You might have to explain that further.|
In any case, if you want to "copy" Rows 7, 14, 21, etc. Enter this formula in Row 1 of any column:
This assumes your original data is in Column A. Adjust as required.
In Row 1, Row()*7 will evaluate to 1*7 or =A7, in Row 2 this will evaluate to
2 * 7 or =A14, etc.
Look up the INDIRECT and ROW functions in Excel Help to see how they work.