What hose is needed to convert to 100 lb Propane tank

Rather than cut the line and "T", unscrew the short line going from small tank to regulator, screw new line into regulator. (Tape over small line to keep dirt and other stuff out) The length of hose you need will depend on your tank placement. By doing your hose this way, when you are ready to move, you simply unscrew line going to large cylinder and screw your short back into the regulator. Any well supplied hardware store should have all of the needed fittings to make it happen.