How do I change captcha?

If I understand you correctly, you would like to change the Captcha field to a reCaptcha. You just need to insert a Captcha field and then click the reCaptcha button at the toolbar.

Also, we have a Google reCaptcha widget. Here's a guide on How-to-Add-a-Widget-to-your-Form.

Please refer to this user guide for more details: https://www.jotform.com/help/205-How-to-Add-a-CAPTCHA-field

Hope that helps. Thank you.