Well I want sand trooper how can I get it or what the best way to get it

Sand Trooper as in the guy with the orange shoulder pad from the OG movie?  He isn't a playable character. 

You may mean Shore Trooper?   He's available on Light Side 9B, hard.  You may not have that unlocked yet.  I think he's still available in shipments from time to time, maybe in the Cantina?

I'm not sure he's that useful anymore to make a priority.  Sure, he's a darkside pre-taunt tank but......Empire teams other than Iden Versio don't really use a pre-taunt Imp Trooper.  The one team that might find that useful is a 'SEE'  team, and a Sith Empire Trooper does that job better.

You could have mistakenly come to SWGOH and actually want a model.  Google 'hasbro black series sand trooper' for a storm trooper with an orange shoulder pad.