As an example, I have taken some values in column A and B as shown below:
Now I want to replace 8 and 10 with 3 and 5 and want the values in row 4 to remain as they are.
Now if I simply copy 3 and 5 from column A and paste it in column B, then as you can see it will replace 8 and 9 with 3 and 5 and not 8 and 10.
To get around this, just type =A3 in cell B3 and drag it down. If you want to do it all in one go, simply select 8 and 10 and type = A3 in cell B3 and hit CTRL+Enter.
Now as you can see below, this will paste data only into the visible cells.