How are you currently setting the alarm in SmartThings? Is it an alarm thing integration like from Konnected or another alarm hardware/service provider… or perhaps using the SmartThings Home Monitor (STHM)?
If it’s STHM, SmartThings doesn’t directly expose STHM as an integration, but there are some creative approaches the community has come up with to integrate STHM – particularly using Location Mode or Simulated Switches along with Automation Routines.