Hello @tedwu1
Hope you are doing well.
You can right click on the current KW38 SDK in the MCUXpresso IDE "Installed SDKs" view and select Uninstall SDK:

After this, you can install the new SDK by dragging and dropping the SDK zip into the "Installed SDKs" view.
If you already have an existing project based on the previous SDK version, you may be asked to select an SDK for your device and project; please, select the new SDK version from the dropdown menu.
Regards,
Eduardo.