Use the MySQL query
sudo mysql -uroot –p
use koha_library; ("library" Instance Name)
UPDATE items SET barcode = lpad(barcode , 6 , '0');
exit;
This will update all accession numbers to six-digit length numbers with ‘0’ as leading

Case 2
If you want to reverse the above, use the below command to remove all leading zeros in the accession number
UPDATE items SET barcode = trim(LEADING '0' FROM barcode);

Case 3
If we want to delete a prefix character from all books barcode have, for example, ‘GEN’ from all books the command will be
UPDATE items SET barcode = trim(LEADING 'GEN' FROM barcode);

Case 4
If we want to delete a suffix character from all books barcode have, for example, GEN from all books the command will be
UPDATE items SET barcode = trim(TRAILING 'GEN' FROM barcode);

How can we do the same steps for removing lead zeros in accession number of koha is installed in Windows platform?
Koha Community not released Windows version yet. If you are using Koha in windows installed version you have to contact the developed authority not only for this any kind of deep fixing.