Depends. The /index.html suggests you had your site on a different platform before and that there are likely other paths that are also indexed but giving 404’s.
You probably need to do an audit and redirect setup for your original site, and then you’ll know what your options are.
If you just wanted to maintain all of the original paths, except for /index.html then you could;
Add the .com domain to your Webflow site.
Keep the .ca as the default domain.
Setup redirects for specific pages if needed, e.g. /index.html → /