Creo Simulate > Getting Started with Creo Simulate > Configuration File Options > About Unit Settings Option
  
About Unit Settings Option
Use this option to control the default units setting for your model.
pro_unit_sys
Customizes your units settings by controlling the default principal system of units for your model.
PROE_DEF
length = in
mass = lbm
time = sec
temperature = F
In this system, the unit of force is in x lbm/sec (inch lbm second), which is not a common unit.
MKS: meter kilogram second
CGS: centimeter gram second
mmNs: millimeter Newton second
FPS: foot pound second
IPS: inch pound second