To Modify Units in DWG Workmode

Open the Design file Settings dialog ( File > Settings > File > Design File Settings ).
In the Design File Settings dialog, choose the Working Units category.
From the (Linear Units) Format menu, choose the type of units that you want to use: Architectural, Decimal, Engineering, Fractional, or Scientific.
If you modify the units, you must choose a consistent base unit in the Advanced Settings.
(Optional) Select the Master Units.
(Optional) Select the Accuracy.
(Optional) Under Advanced Settings, check the Resolution to make sure that it is compatible with the Format. Specifically, if the Format is set to Architectural or Engineering, the Resolution must be inch-based.
(Optional) If the Resolution needs to be modified, click the Edit button and change the Resolution on the Advanced Unit Settings dialog.
CAUTION: Changing the Resolution can change the size of existing geometry in the model.