@shelleyann25 . The 4353 may be locked to Belong. Do factory reset. When you are trying to enter your TPG details, are you in that part of the router that allows changes to be made or only displays settings? I can't find a manual for this device.
TPG settings are PPPoE, username and password.
Your NBN connection type seems to be FTTP. If you need to buy a router, you might consider one which also has RJ11 DSL port in case you move to an apartment/house with FTTB/FTTN.