Looks like you are in need of the VLOOKUP formula.
1: the cell/value you want to lookup. The barcode from sheet2
2: the matrix you want to look in. All the data from sheet1
3: the column you want to retrieve info from. For description 2, for quantity 3.
Select the matrix in the formula and hit F4 to make the reference absolute, do this for easy dragging.
Please post back if you get stuck (or to say thank you).