I have two columns, A and B and I need to figure out a function that puts a number into column C based on A and B columns.

I am doing an excel assignment and having trouble figuring out a function. I have two columns, A and B and I need to figure out a function that puts a number into column C based on A and B columns. For example, if row A and B both have 2 then column C has 4. I have 285 rows, is there a way to set all columns with 2 and 2, or do I have to go row by row and change the function? So confused.