I need a new W2 form from my employer because it is not correctly filled out and I don't know who to contact to get one

You will have to find that out at work.    If there is a payroll department that is who to ask  --- or maybe human resources.   Or ask your immediate supervisor how to get a corrected W-2.  What is wrong with it?

What is wrong with your W2?  Maybe something just doesn't make sense to you and we can explain it.  Is it saying your employer took out too much Social Security Tax?

They have the numbers swapped for everything in boxes 1-6. I also have no contact to the company. I no longer work there due to personal reasons.