Financial Statement Lookups

Hello. I have a tab that has monthly financial data for various items based on an old report. I would like to transfer all of that data into a new tab with the updated items from the new financial report. At the same time, I would like to check if there were any items from the old report that are not included on the new report (I don't want to leave any data behind). Does anybody have any recommendations about lookups that I could use to accomplish this? Thank you!!

Just to clarify, the items in the new report are the same (I believe) but the ordering and formatting is different. Additionally, the month is in the column and the item is in the row. Thanks again