Use your own records or records available to you and enter the income as 'cash' when you go through your Schedule C Business Income and Expenses.
This would be considered to be self-employment so you would use Schedule C to report the income and any expenses you had for the work.
Use the information in the following TurboTax help article to get started:
Where do I enter Schedule C?
**Say "Thanks" by clicking the thumb icon in a post
**Mark the post that answers your question by clicking on "Mark as Best Answer"