Hi @divyaprince321,
I've made this PM public as the answers may help other users in the future who might have the same inquiry.
Have you seen the importing tutorial yet? If not, this section on importing .fna files seems especiallly relevant to what you are trying to do, pay close attention to the --type parameter there compared to what you have here.
In the future, providing us with the actual error will also be necessary to troubleshoot further. Good luck!