How to append two tables when we have different column names?

I have a columns like week18, week19, week20, week21, week22, underneath each column I have customer qty and buyer as sub column headers in table1, same way I have columns like week19, week20, week21, week22, week23 underneath each column I have customer qty and buyer as sub column headers in table2 as well, these files I will receive on weekly basis so column headers will keep moving forward to next WeekNo and so on. These files are stored in SharePoint folders. Requirement is that i want to append these tables and prepare a output report which includes those all week columns as single column as "week" And underneath wk-18, wk-19, wk-20, wk-21, wk-22, wk-23 to those corresponding customer qty and buyer values. I am facing challenge in handling week (date) columns as it's weekno keep moving forward and we end up getting to different weekno columns and not sure like which weekno belongs which value. Can you please help me to find a solution for this?