Four grid reference questions ?

1. What is the grid reference for a location at the intersection of the 5th row and the 3rd column on a grid?
2. What is the grid reference for a location at the intersection of the 10th row and the 8th column on a grid?
3. What is the grid reference for a location at the intersection of the 2nd row and the 6th column on a grid?
4. What is the grid reference for a location at the intersection of the 7th row and the 4th column on a grid?

How I don't understand