Statements:
1. All the boxes contain books.
2. Some of these boxes have also note books.
3. Some other boxes have also scribbling pads.
Conclusions:
I. Some boxes contain only scribbling pads.
II. All boxes contain note books.
III. Some boxes contain note books and books.
IV. Some boxes contain note books, scribbling pads and books.

Statements:
1. All the boxes contain books.
2. Some of these boxes have also note books.
3. Some other boxes have also scribbling pads.
Conclusions:
I. Some boxes contain only scribbling pads. (Not Follow)

All boxes contain books. So, no box can have only scribbling pads.

II. All boxes contain note books. (Not Follow)​

The statement says some boxes have notebooks, not all.

III. Some boxes contain note books and books. (Follow)​

Since some boxes have notebooks, and all boxes have books,
Therefore, some boxes contain both notebooks and books. 

IV. Some boxes contain note books, scribbling pads and books. (Not Follow)​

We know some have notebooks, and some have scribbling pads,

But it is not stated that any box contains both notebooks and scribbling pads along with books.

So, Only Conclusion III follows.

Thus, correct option is (b).