Alternative int range

Hello, this is Mahsa

I have issue that is , I wanna set some slider range in script like between 3 to 12 (int), and i want to go like 3,6,9,12 not 3,4,5,6…

thanks

For this, you would have to write your own PropertyDrawer.
Have a look here: Unity - Scripting API: PropertyDrawer

The lowest two code snippets show you how to a) make a new PropertyAttribute that you can put on top of your serialized field, and b) how to add an editor class that defines what you see in the inspector.