What is the value mot_thst_expo value for 3 inch propeller

am using T - motor f1507/kv2700 prop 3140 (3.1inch ) for this specification what is the value of mot_thst_expo value can i set

In Mission Planner connect to the craft and select Alt>A. Enter prompts and see suggested values.

dear dave
can u explain clearly

1-open mission planner
2-connect to flight control
3- press Alt+A key at the same time
4-it will ask you about propellers size and battery cell count
5-after entering required data it will show you mot_thst_expo and other parameter for first time setup

Thanks for replying @hosein_gh