I didn't see an SRX template yet that was build for SNMPv3. I will update the template when I find new values that seem important.

Kudos to the creator of this template for providing a good baseline:

https://share.zabbix.com//network_devices/juniper/juniper-srx-series

Do not forget the add the macro's:

User: {$JUN_V3_USER}

Password: {$JUN_V3_AUTHPASS}