There is no code to type in.
You have to recover a new fuel rod for the saucer, and then the instruments will let you use the X and Y dials to set the coordinates. But the planet coordinates the Queen gave you are too far away. You will need to use the coordinates from Mordred's missing journal page, which are X-56 Y-52.
(see related question)
you have to find the UFO in astro knights island.
x-56 y-52 it will get you to the moon. the moon is the only place you can go on the flying saucer
This means you have already completed the Arturus part of Astro Knights Island. Your spaceship should be parked on top of the castle if you return to the planet.
Saturn star moon
Yes, anytime you are back on the Pewter Moon.
When your on the moon just jump to the big building and he is inside.
press the moon button then figure out the combination
On the Pewter Moon, see the manager at AstroZone about replacing your ship.
get the fuel and put it in the rocket ship and put in 56 and 52.
The only coordinates that you can enter (once you replace the green fuel rod) are those for the Pewter Moon, which are X-56 Y-52.
In Poptropica's Astro-Knights Island, to find the Fountain Code, you need to retrieve the missing letter from Mordred's room. Once you get the missing letter, use it to decode the message and obtain the code for the fountain in the Knights' Chamber. Use the code to unlock the fountain and progress in the quest.
You must enter the Astrozone building and swap your saucer for a new ship, which you build on the Holopad.