How do I change default units?

[aread]

I want my Mathcad Prime 3.0 sheet to auto populate using a different unit than the default unit system. For example I want all my answers to be in mm (millimeters) instead of m (meters). Can I change the default so I don't have to type "mm" into every answer manually?

Thanks

[ValeryOchkov]

We can do it only in old Mathcad

[JR_9927623]

Well, I've just installed Prime 9 and still no way of doing this, What a pain in the behind!