Hi Srivaths,
Check in Transaction TPM_MIGRATION_CAT if you can see the this conversion category 7. If yes set it up and try to do a migration after you set all the old transactions/positions in the tables i mentioned before.
If migration is not possible, go to tcode TPM56a and manually assign all the contracts/positions to relevant Funds/Grants. After that you shouldn't get the error.
Regards,
Nikhil