The land transfers with the County Recorders office. Some mobile homes transfer with the DMV, some do not. I believe the difference is the year built. So check and see if it is registered with the DMV if not probably the county recorders office may be all you need.
Check with the Assessor - County Clerk - Recorder's office for the county the property is located in to obtain the correct forms as well as filing instructions, and locations at which you can file the forms.