Some portables can be converted to an in-ground system depending on the mounting of the backboard. This would require purchasing an in-ground pole system. This is because in-ground systems and portable systems use different pole kits.
The only parts you would use from the portable system would be the rim and backboard. To find out if your system can be converted, please call +61 1800 632 792 (Mon - Fri 9 am - 5 pm AEST) with your model number and a representative will assist you.