System Preferences for Time Machine

open /System/Library/PreferencePanes/TimeMachine.prefPane

will do it. But, I'm not sure how well the above will work when its executed from a policy that is triggered in a root context, instead of by the user. You might need to use one of the known tricks to get the command to run as the logged in user. I haven't tested it via a policy, so I'm only making a guess on that. Try it and see.

worked perfectly! also within a script policy!

If you want to open the preference pane, maybe you even want to configure Time Machine settings?
use a profile (help online) , or use the tool 'tmutil' see

man tmutil

for help