We cannot let you know if you will need a CNI to have hitched. You need to ask the authority that is receiving

Certificates of No Impediment to wedding (CNI) We are able to issue Certificates of No Impediment to Marriage (CNI) overseas. Quite often, you may not require it. Nevertheless the authority that is receiving ask you for any other papers from Australia. Including Solitary Reputation Certificates, No Record Result Certificates and Divorce Certificates.