What is the JUNOS equivalent to a MIP in ScreenOS?

The equivalent to a MIP in ScreenOS is called a Static NAT in JUNOS.

The method of creating a Static NAT differs depending upon the version of Junos:

Flow-based Junos versions

• JUNOS 9.4 and above
• JUNOS with Enhanced Services 8.5 through 9.3

• Technical Documentation Static NAT example: http://www.juniper.net/techpubs/software/junos-security/junos-security10.0/junos-security-swconfig-security/configuring-staticnat-srx-example.html#configuring-staticnat-srx-example
• Technote with examples mapping NAT in ScreenOS to Junos: TN25 - Configuring Network Address Translation (NAT) on SRX and J Series devices [for ScreenOS Users]
• SRX Getting Started - Configure NAT (Network Address Translation):  http://kb.juniper.net/KB15758 [juniper.net]

• JUNOS 8.4 and below
• JUNOS 8.5 through 9.3 (non-enhanced services)