Hello,
You're on the right track. Just missing one step.
In TextEdit, go to the "Format" menu. Then choose "Make Plain Text".
Now, go to save (or Save As) and save your document.
Now, you'll have a Plain Text document.
I hope this helps.
Let us know if you have other questions.
P.S., if you'd like, go ahead and click the "Helpful" or "Solved" buttons on any of the posts / replies above if you feel they were helpful or adequately answered your question.