How can I change from inch to mm?

There are a couple of ways but it is best to use the right template to begin with.

If you get the wrong units by accident, in Creo, have the part or assembly open; go to file>prepare>model properties>units and select>set the units you prefer. You will be asked if you want to convert or interpret the dimensions. the dialog will explain what will happened for each choice.

There will be a lot of other options to configure drawing parameters, but this will get your part set to metric units.

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