how can i make the form go to the top of the page to see the thank you after form submission

Embed your form using Iframe Embed Code. http://www.jotform.com/help/148-Getting-the-Form-iFrame-Code

Iframe has an auto-resize feature so I believe the form length will shrink down once the form is submitted which makes the form thank you page visible on the screen without a need to scroll down.

Let us know if this doesn't help.