Extract private key without password. The first command will request pfx password and prompt for a password for key.pem; a password for key.pem must be provided. The second command asks for key.pem password provided for 1st command.
openssl pkcs12 -in cert.pfx -nocerts -out key.pem
openssl rsa -in key.pem -out server.key
openssl pkcs12 -in cert.pfx -clcerts -nokeys -out cert.pem
Extract certificate chain:
openssl pkcs12 -in cert.pfx -nodes -nokeys -out chain.pem
Certificate chain contains several items. You may need to remove item that refers to your certificate, it's on top and it's not needed. Give a try with/without removing the top item. After that, the other items should be placed in reverse order.
server.key is a private key in ELB, cert.pem is a certificate in ELB, output #4 is certificate chain.