Matching to sets of data

Hi
I have 2 sets of data. Each set contains 2 columns, company names and their account numbers. There many companies and their account numbers in the first set, but in the second there is a selection of company names (the same companies in the first set) without their account numbers. I want to enter their account numbers in front of them (account numbers should come from the first set). Because there are many rows I can't do it manually. I need a formula to match these two sets of data and automatically enters the account numbers in front of a company names. (I attached an excel file to explain how I want to match data in these 2 sets).
Thanks a lot

Thank you so much
Now if I want to match 3 first characters instead of the whole name what changes should I make in the formula?