Sorry to hear that the website was hacked but I am glad to hear that it's backup again.
I suggest you to first take a complete backup of the website. After that, if you have made changes to theme files without installing child theme then please install child theme and move all the changes into child theme.
Next, please revoke validation from Pro > Validation > Revoke Validation. After that deactivate and delete Pro from Appearance > Themes and download a fresh copy of Pro Theme. Next step would be to Install and activate Pro from Appearance > Themes > Add New > Upload Theme.
Finally, from Pro > Validation enter your purchase code to validate Pro Theme.
I am sharing few resource that can be used to download and setup child theme:
Please let us know how it goes.