Thanks @sureshkrishnan-mr, however we would need to know the real values involved to test this properly. Could you please create a fake user on your original system, and share with me the original hash and salt, the associated password you used for the fake user, and a sample import payload you would use to try to import it into your tenant?
What would also be very useful to know is the code that is used currently to verify your passwords. For example, you are currently using a prefix, but your shared code grabs the first part for the hash value and the second for the salt if I am reading it correctly. Is it the opposite way around on your original DB?
You can send this information in a direct message to me if you prefer not to post these details.