Plant 3d switch units

Hi, 

i'm using a valutation version of plant 3d. I canghed all the units of dwg to millimeters, but when i design the input is always in imperial units. 

I see this becouuse for ex. the diameter of a 3" pipe misured with command "dist" results 3 instead of 89, and when i design a pipe length of 3 it results of 3" and not 3mm.

What i need is to inser lengths in millimeters.

Thank you all.

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