Christopher - see this answer to another question by Courtenay Shipley.
I wrote a guide on this recently. You might find it helpful: https://www.brightscope.com/financial-planning/advice/guide/10268/Guide-To-Tracking-Down-Old-401K-Accounts/
You should call your former employer's benefits or human resources department. They should be able to provide you with the contact information.
If your employer no longer exists, then you will need to do some research. One
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