It sounds like you have fe-0/0/7 defined as “family inet”, but it sounds like you want to configure it for “family ethernet-switching”, “port-mode trunk”, and add the vlans with “vlan members”. You will also have to add the new “vlan interface” to a security zone.
(Without seeing your config, this probably won’t be a direct “copy and paste” into your config, but it should give you an idea of what would be required.)
set interfaces fe-0/0/7 description “Trunk Interface”
set interfaces fe-0/0/7 unit 0 family ethernet-switching port-mode trunk
set interfaces fe-0/0/7 unit 0 family ethernet-switching vlan members Home
set interfaces fe-0/0/7 unit 0 family ethernet-switching vlan members HyperV
set interfaces fe-0/0/7 unit 0 family ethernet-switching native-vlan-id 3 <<sends untagged packets to Home VLAN, may or may not be needed for your config
set interfaces vlan unit 3 description "Home VLAN"
set interfaces vlan unit 3 family inet address 10.0.20.1/24
set interfaces vlan unit 4 description “Hyper-V VLAN"
set interfaces vlan unit 4 family inet address 192.168.1.1/24
set security zones security-zone Home interfaces vlan.3
set security zones security-zone HyperV interfaces vlan.4
set vlans Home vlan-id 3
set vlans Home l3-interface vlan.3
set vlans HyperV vlan-id 4
set vlans HyperV l3-interface vlan.4