How to get user FNAME and LNAME on thanks page.

Hi,

I want to show user FNAME and LNAME on the thanks page.

I have gone to the Dashboard -> Mailchimp for WordPress -> Forms-> Settings -> Redirect to URL after successful sign-ups and entered the below URL in this field.

https://uptownfitnesscenter.com/thank-you?FNAME=FNAME

But, I’m unable to get the FNAME.

Thanks for the help!