Hi Abdel! If you download a fresh copy of the theme, you can copy style.css from that.
On that note, please be aware that if you’re editing the theme’s CSS directly, you may lose your changes. Updates would overwrite what you have with the latest copy of the code.
I’d recommend downloading a fresh copy of Orvis and comparing its style.css with the modified version you have. Then you can port your changes over to Customize > Additional CSS, where they won’t be overwritten.
Or, if you’ve edited the theme’s PHP files as well as its CSS, you may want to consider creating a child theme instead. More info here:
https://developer.wordpress.org/themes/advanced-topics/child-themes/
Hoping this helps!