Field definitions for existing metafields
Just as well as ACF lets you define fields in discrete namespaces to keep it from updating metafields from other apps, you can also use it to handle metafields defined by other apps.
ACF features an easy-to-use wizard to find existing metafields created by other apps and will automatically reuse any existing values once a defintion is in place.
From with the field definition dialog for each scope, click the "Add field" button near the top:
This will open the field definition wizard:
Click the "search" icon to the right of the "Name" field to open an additional wizard:
Here you can select a single object (a product in this example) to inspect for existing metafields not already defined in ACF. You can click on a "Name" field to return to the field definition dialog with that name and namespace filled in. Now you can add your preferred Label and in the next steps, select a type as well as other options offered by ACF.
Be sure to select a type and configure it with the existing values in mind. You can never go wrong with a Text or HTML field but if in doubt of which field type you should select for a given set of existing fields, please get in touch for assistance.