Set option by url variables

I have a classic select dropdown menu from forminator with 6 options. And I have an url variable called button. This variable usually stores integer numbers 0 – 6.
I would like to know how can I select an option depending to value of this variable. If variable button would be 1, second option would be displayed on the select dropdown menu.
Is this somehow possible?
Thanks for any answer.

The page I need help with: [log in to see the link]