In many cases the imported data has a property that stores the Z elevation for each feature. This property can be selected by using the pull down menu in the elevation field. Active depth values for each view can also be selected.

The example above will place all contours at the value specified in the ELEVATION property.

Expressions can be added to the Elevation parameter. For instance if the value of the property was feet, it could be converted to meters by multiplying by 0.3048.