Merging Excel Documents

Hello Everyone!

I need help.

I am currently working with two documents for a project for work, one organized with a list of 21,000 product upcs to correspond to product numbers and what I need to do is somehow merge that into a list of 17,000 (of the 21,000 upcs) I was just given. On the list of 17,000 I need to somehow transfer the corresponding product numbers from the first file.

Is there anyway to do this by not doing this one by one and keep the information matching up?

Thank you!

To make this easier to understand, I can put the two columns I need into another excel sheet but then I need to match them up:

Current:
Column A Column B
A1: 1 B1: 4
A2: 2 B2: 6
A3: 3 B3: 2
A4: 4 B4: 7
A5: 5 B5: 9
A6: 6
A7: 7
A8: 8
A9: 9
A10: 10

Need:
Column A Column B
A1: 1 B1:
A2: 2 B2: 2
A3: 3 B3:
A4: 4 B4: 4
A5: 5 B5:
A6: 6 B6: 6
A7: 7 B7: 7
A8: 8 B8:
A9: 9 B9: 9
A10: 10 B10: