I hope this is the correct place to ask this question which entails asking if there is a database much like the JPL NASA one for the solar system, but for exoplanetary systems? I am conducting an n body simulation as in the assignment it states "Study the stability of known exoplanetary data. You will need to look up the available planetary data." But from what I have seen there is no such data easily accessible. For my simulation, I input the mass, initial position and initial position. Is there a website or database that could help, I have seen data on these systems such as mass and the radius of the orbit, but that would be estimating the initial velocity and starting positions which I didn't deem the most scientific. Any thoughts or ideas are much appreciated.
One of, if not the most comprehensive exoplanet table is found at exoplanet.eu which also lists the angle of the ascending node and the time of perihelion, time-of-transit, stellar data etc as far as these data are available including references to the papers the data are taken from.
You can download that convenient as csv for processing.
The only currently possible way I see here is indeed taking the mass of the central star, the radius of the orbit (assuming it is circular ) of the exoplanet, and calculate initial velocity. After that randomly distribute as many planets, as you want to have in the system, over the initial position vector angles. Depending on your task, you may want to add only known planets, or add some more. Also, in reality, planets do not have a "starting position". They were formed for hundreds of millions of years while doing many revolutions around the star.