Have a check on the motherboard to see if there are any voltage markings, e.g. “+12v”, “Ground”, etc. next to the PSU pins. Without knowing what voltage goes to what pin, it’s extremely risky to try guessing what voltage goes where. The wire colours generally don’t dictate voltage either, e.g. a green wire could be a totally different voltage between one power supply and another. For example, if you attach a wire with 12v to a pin that takes 5v, it will likely permanently blow the motherboard along with just about anything attached to it (RAM, HDD, etc.)
If you don’t see such markings, try dismantling the “black box” part of the broken power supply to see if the wires are voltage marked at that end.
Otherwise I would suggest picking up a cheap charger off eBay for that laptop and using a multimeter to check the voltages of the pins, so you know what voltage goes to what pin on the laptop’s PSU connector.
Once you do have it wired, install the bare minimum hardware necessary for the laptop to turn on, i.e. a single low capacity stick of RAM and leave out the HDD and don’t attach anything to any USB port. This way if a pin is miswired, you minimise what could be blown.