At 81, my husband left his government job and the Georgia Defined Contribution Plan (GDCP) refunded his money. Is that taxable income, or do we only owe on the interest?

The ERSGA (Employee Retirement System of Georgia) who refunded us says they can’t tell me what type of plan it is, such as a 457b or 403 b, and the IRS says I need that information to find out what part is taxable.