You can ohm the wires to determine which wire go to each of the windings. There are 6 windings in a motor.
How many wires does your motor have?
Some 3 phase have 9 wires some have 12 wire.
What is the frame size and physical size of your motor?
Look at WW Granger online match your motor up with a new motor frame. Physical size & shaft diameter will tell you what you have.
American motors are 240/480 vac 60 HZ. Canada is 50 HZ.
There are some 550 and 600 vac motors.
Coal mine motors are 5000 vac.
You can start & run your 3 phase motor on single phase with a capacitor. Once you get it started check idle current that will tell you the HP check idle current for other motors. Capacitor needs to be 60 MFD per HP use only a motor START capacitor with a push button N.O. switch to put cap across L2 and L3 for 3/4 of second until motor starts. Voltage across L1 and L2. Check current across L1 or L2 when motor is running with out the capacitor.
Capacitor size is not critical. If you can find a motor on WW granger with your frame size and shaft diameter that will be very close.
Example. Assume you think your motor is 5 hp because shaft diameter is same as a Granger motor. Cap needs to be 60 x 5 = 300 mfd. If you try 300 and motor will not start then try 400 and 500 and more if needed to get the motor to start. Remove cap at once when motor comes up to full RPM. Now that motor is running use an amp clamp to read idle current on L1. Check motor RPM too. Compare, motor shaft diameter, voltage, amps, RPM to new motor specs.
Checking idle current is more accurate than full load current because most motors can deal with short over loads like 20% for a short time like 5 seconds before the correct circuit breaker trips and turns the motor off. 3 phase motor tags show, idle current and full load current on both voltage 240/480. You say you have no tag so if your idle current is 12 amps on 240 volts and you find a new motor specs that say the same thing with same shaft diameter and same RPM it should be the same HP as your unknown motor.
There is another way to start a 3 phase motor. Connect a single phase motor shaft to the 3 phase motor shaft with, a shaft coupling or V belt pully also called shives. Start the single phase motor when it comes up to full RPM turn on the 3 phase motor and turn off the single phase motor. 3 phase motor will run good with voltage on L1 and L2 only. 3 phase motor RPM can be, 1725, 1400, 1200, 1100, 1000, 900 so check it with an RPM gauge. Low RPM motors are used for hydraulic pumps it keeps the pump from sucking vacuum bubble in the oil.
You can also start a 3 phase motor with a rope. Wrap a 1/8" diameter rope around the motor shaft 15 times with the motor bolted to a work bench pull hard. If you can get the armature up to about 600 to 800 Rpm it will start when you turn on the voltage.
What voltage and HZ do you have in Australia. Home voltage in USA is 240 that is the only choice we have at home in single phase unless you have a step up transformer or industrial variac.