Hi Abdul Rochim,
You can find some notes here and you can configure the 2048 DH modulus for ssh key agreement (dh-group14-sha1) using the following command :
#set system services ssh key-exchange dh-group14-sha1
Also, don't forget to configure SSH v2 and block root login ( after you create another administrator user to login with ) :
#set system services ssh protocol-version v2
#set system services ssh root-login deny
There is this book on hardening JunOS devices ( Edited : You'll find on Page 73 the FIPS certified ciphers and MACs you should use ).