The area of a square is calculated using the formula:
\[ \text{Area} = \text{side length}^2 \]
For Square A, each side measures 5 units. So, the area of Square A is:
\[ \text{Area of Square A} = 5^2 = 25 \text{ square units} \]
When Square A is translated to form Square B (4 units to the right and 6 units up), the side length remains unchanged. Therefore, Square B also has a side length of 5 units.
Now we can calculate the area of Square B:
\[ \text{Area of Square B} = 5^2 = 25 \text{ square units} \]
Thus, the area of Square B is:
\[ \boxed{25} \text{ square units} \]