In my knowledge, on the MX/vMX devices we have bridge domains instead of vlan. The below configuration might help you in understanding the steps to establish reachability between different VLANs (bridge domain) :
set interfaces ge-0/0/0 unit 0 family bridge interface-mode access set interfaces ge-0/0/0 unit 0 family bridge vlan-id 10 set interfaces ge-0/0/1 unit 0 family bridge interface-mode access
set interfaces ge-0/0/1 unit 0 family bridge vlan-id 20 set bridge-domains vlan-a vlan-id 10 set bridge-domains vlan-b vlan-id 20
set interfaces irb unit 10 family inet address 10.10.10.1/24 set interfaces irb unit 20 family inet address 126.96.36.199/24 set bridge-domains vlan-a routing-interface irb.10 set bridge-domains vlan-b routing-interface irb.20
Please mark "accept as solution" if this answers your query. Kudos are appreciated too !