Depending on your "use case", you may want to reach out to your area ST.
SDM3000's are - usually - seen as the endpoint for MCC7500 Aux I/O's.
In other words, they allow the console to open say garage doors.
It requires a specific firmware load that can be done via the web interface
on the device. The I/O ports can then control external relays. Also
specific programming in PM is needed to enable those ports/functions.
RTU usage is more complicated. Typically seen at RF sites. You need
SDM Builder to create a codeplug to download to the device. Lots of
information is needed to build that file. It will also report status to
UEM and possibly other applications (ie. moscad/gws for control of
the devices connected to it). UEM discovery will be needed - which
means SDM Builder SNMP settings need to match what you use in
UEM. Lots of little details that if you've never done it before, you're
better off offloading it to the ST assigned to your territory.
As for SNT (network translation), *big* caveat here - if your box was
ordered from the factory as an SNT only - then you are SOL - they were
not usable as an RTU because the I/O option boards were not installed
in an SNT only SDM3000 (that might have changed, but last time I did
one, they were missing).
No further support offered.
Good luck.