how to change the default units inches into mm in solidwork

Step 1 :- Open a New Part File in Solidworks
Step 2 :- Now click on Options
Step 3 :- Now check under Document Properties & click on Units
Now change the default Unit system to your desired unit system
Step 4 :- Next step is to click on Save button
Step 5 :- Now change the file Save As Type to Part Templates
Step 6 :- Now click on the Original Template File & press Save

So now you have PERMANENTLY changed your Unit system
Note that the similar procedure is also applicable to Assembly and Drawing Files...

very easy, go to options on the main toolbar select document properties tab -select units from the drop down menu - click on unit type and set number of required decimal places etc. I normally set them to 4 places of decimals

or click on the MMGS tab at the bottom RH corner and select unit type

Thanks Aniket Gaunkar. its working and will expect Ur help in future.

Thank You Aniket Gaunkar! That was super easy to follow, and now, I'm going to save a lot of time by not re-changing all the unit specs for every new part I make.

I just wasted an hour of my life trying to figure that out.

You sir are a legend, thank you.