How to download an MIB for a specific version.
Management Information Base (MIB) is a database of objects that can be monitored by a network management system. The Simple Network Management Protocol (SNMP) uses standardized MIB formats that allow any SNMP tools to monitor any device defined by a MIB. Juniper Networks provides MIB files to support SNMP communication between your organization's applications and the SNMP agent.
Using the following link you can get information about various MIBs, MIB Objects, and SNMP notifications supported on Juniper Networks devices. https://apps.juniper.net/mib-explorer/