In this tutorial i will show you how to change units permanently in Solidworks.
Open a new part file in SolidWorks.
Go to options.
Click on document properties, click on units, change the default unit system as you want, and then click OK.
Go to the file menu and click Save As.
Choose a name to your file, change the save as type to part templates (*prtdot), and then click the save button.
Go to option, click on system options, click on file locations, click on the Add button, choose templates, and then click OK.
open a new part and click on the Advanced button.
now you have Permanently changed your Unit system
Note that you can follow the same steps with the Assembly and Drawing files.