Can you help me with question on gas line?

unless it is VERY old mobile homes are manufactured to meet the requirements for natural gas, By doing this they can function on either. The main line hook up is black pipe at the home and is usually labeled on the bottom edge of the home as to where it is located. it is possible that the supply line to the home is to small because they were piping for propane or LP. when they convert the supply to natural most likely you will need to run a short section of copper line to the home from the meter location. depending on your local building codes it may be possible to perform the hookup yourself.