Also, I would suggest that you use just a normal gallery and not the Wix Pro Gallery if you are wanting to implement any code with it.
Wix Pro Gallery is a Wix app and has it’s own Wix Support section that you can read through.
https://support.wix.com/en/the-wix-editor/pro-gallery
Plus, have a read of this previous forum posts about similar issue.
https://www.wix.com/corvid/forum/community-discussion/problem-using-wix-pro-gallery-and-dynamic-pages