First of all, turn on Unity support for Serial Port:
Menubar → Edit → Project Settings → Player → Inside “Inspector” window on the right → In “Settings for PC, Mac & Linux standalone” tab → Under “Configuration” → Change “Api Compatibility Level” from “.NET 2.0 Subset” to “.NET 2.0”
Force-Sensitive Resistor on Pin A0
Two servos on Pin 9 and 10