Want to change all dimensions in a file from Inch to mm.
Solution
The easiest way is to go into the style being used in that file for the dimensions, go to the Units tab and change it to mm there. This might be confusing, though, if the style is "ANSI (inch)" and shows up as metric in that file. You could also use SmartSelect to pick all dimensions on a sheet and change them with Edit Properties to a different style (ANSI (mm), for example).
Notes and References
Hardware/Software Configuration
Platform: INTEL
OS: windows
OS Version: 1064
Product: SOLID_EDGE
Application: DRAFT
Version: V220MP8
Function: STYLES
Ref: 001-9858567