Hi Akesh,
As Srinatha said, really you are doing a huge cleaning and I am doubt about the closing the order after KB11N re posting, until unless your balance become zero through settlement system wont allow you to close the order (CLSD), Please test this scenario in your test system, If it is allowing, then you have to create a BDC for KB11N for mass upload.
All the best for you to initiate this process.
Regards,
Ravi