You can do a copy and replace.
So highlight the cells you want to change, and do a Ctrl-F and replace the value according.
However this might have side effects you might not desire.
For example lets say you want to change 3 to 10, then you might actually change cell B3 to B10, B30 to B100 etc. . .
Your best bet is to make a constant by having all the values represented in another cell.
For exmaple A1 then your formula will look like
$A$1 * B1
$A$1 * B2
$A$1 * B3
Then you just change A1 and all your forumlas update accordingly.
($ means don't change the cell either column or row after when I do a drag or fill. In this example A and 1 do not change.)