Beginner trying to compare cells in two columns and copy a third column if it is a match

Hello, I am a beginner at this so please excuse me if I don't make myself entirely clear but Ill try!

I want to compare two columns of cell values and when there's a match, a value from a third cell in a third column needs to be copied to a fourth column, right next to the first two columns.
I am ordering items from a company and I want to match their product number to the amount we want to order. Our ordering systems puts out an excel sheet with prod number in one column and amount we want to order in the column next to it., I want to match two columns containing order number (our systems and the official order form, they use the same formula) and then add our column of "amount ordered" should be added to its respective item row.

I suspect using MATCH or INDEX is a start but I haven't been able to get it to work.