[Koha] data migration from libsys to koha

Dear All, I want to data migration from libsys to koha, My current state is that I took backup from libsys in iso format and convert it in .mrk files. Now my problem is that it shows tag numbers like 999 964 etc. When I tried to import .mrc files in koha by script bulkmarcimport in koha/bin/migration directory, it imported data but did not show 900 series tags. And it is not proper shows all information like accession numbers etc. That is my current status. Can anybody help me to properly tag mapping for koha in .mrk files. So that it can take all the data while importing properly. Any help will be helpfull regarding tag mapping from libsys to koha. Thanks in advance. Regards Amit