How can I find a retirement plan I had 20 years ago if the company no longer exist.?

Answer 1

The company the plan was with or the company you worked for?

If you had a retirement plan and it survived your leaving the company, you should have received an annual statement of the balance. If you failed to tell them you moved, the money would have been turned over to the state where it was located, and you can check the unclaimed funds list, usually at the secretary of state (for the state, not the US) where the plan was located. After 20 years, you may not be able to claim it.