The best place to start is here:
All the new Juniper switching products, EX4300, EX4600, QFX5000 and 10K series all use a slighty different CLI, referred to as L2 ELS, for some config areas, which is similar to what MX uses. Instead of using L3-interface vlan.9 you use instead irb.9, and then you must define the irb interface.
irb is the terminilogy, versus vlan for L3, although vlan still used for L2. You can also use the ELS translator (link is embedded in the above URL) to translate set vlans name l3-interface vlan.9 into
set vlans name l3-interface irb.9
You could take your EX4200 style config and use translator to convert to new ELS format. ELS will the CLI choice on all new products going forward.
This is called out in the docs.
Hope this helps, and Good luck.