I want to make a square with the scale of "8.1". The square should be hollow and inside the square are 81 other smaller squares with the scale of "0.3"
Is there a way to automatically do this without manually doing it?
You can use Array Modifiers to create all the small squares.
First create the big square (insert a plane) and set the appropriate scale using the object settings.
Then do the same for one small square. Do not move it yet.
Then add an Array Modifier in the modifier tab. Set it to make x copies. Apply the modifier.
Rotate the new planes 90 degrees along Z.
Now add another Array Modifier and set that to make x copies in the other direction.
Now you will have to delete one plane because 27 is not an even number.
The reason I said X copies (I didnt give you an exact number) is because nothing multiplied with itself is 27. ((EDIT: Original question proposed 27 squares)). You could for example make 3 copies in the X direction and 9 in the Y direction.
-Unless you actually meant Cubes, (not squares), in which case 3x3x3 should do the job for you. (you will have to add another array in the remaining direction.)
You will also have to play around with the Relative Offset settings of the Array Modifier to get the correct spacing. If you want spacing.
EDIT: Alright, if you want 81 squares you can use two array modifiers with nine copies each. 9x9=81 I hope that helps.