i belive im supposed to use the product rule. but i cannot seem to get the correct answer.

Always post all your work. Not only does it make it easier for us, but it shows us exactly where you went wrong.

How far is the electron from the origin when it momentarily stops?

You need to find out when it stops, aka when velocity is 0. So to find an equation for speed, you need to take the derivative of the distance (location).

It sounded like you already knew that, so what are you having trouble with? Just taking the derivative?