Answer:
I. 6 cells . 
II. Series connection. 
Explanation:
I. Determination of the number of cells needed. 
From the question given above, 
Total voltage (V) = 9 V 
1.5 V = 1 cell
Number of cells needed =?
The number of cells needed to make the 9V battery can be obtained as follow:
1.5 V = 1 cell
Therefore, 
9 V = 9 V × 1 cell / 1.5 V
9 V = 6 cells
Thus, 6 cells of 1.5 V each is needed
II. Determination of the connection line
Total voltage (Vₜ) = 9 V 
Cell 1 (V₁) = 1.5 V
Cell 2 (V₂) = 1.5 V
Cell 3 (V₃) = 1.5 V
Cell 4 (V₄) = 1.5 V
Cell 5 (V₅) = 1.5 V
Cell 6(V₆ ) = 1.5 V
For parrall connection:
Vₜ = V₁ = V₂ = V₃ = V₄ = V₅ = V₆
9 V = 1.5 V =... = 1.5 V 
For series connection:
Vₜ = V₁ + V₂ + V₃ + V₄ + V₅ + V₆
9 = 1.5 + 1.5 + 1.5 + 1.5 + 1.5 + 1.5
9 V = 9 V 
From the illustration above, we can see that series connection of each cells will give a total volt of 9 V unlike the parallel connection which resulted to 1.5 V. 
Therfore, the cells should be arranged in series connection