how to display grid that display whole number from 1 to 9? how to detect player touch the grid?

How to display grid that consisits random number from 1 to 9..this number can be repeated ..for example the grid 4x4 which consists number from 1 to 9..and when user press the number , the number will be put to array..user can press number more than one..the number pressed will do addition to get the sum of number pressed..for example 4+3=7..3+3+3=9..I already create the grid by using prefab then i duplicated it..is it the right thing to make it like that or do i have to create layout script to place the grid..I a bit lose here..I'm new to the unity..