Short answer is that you can’t. The problem is that the old plugin you used stored multiple values in multiple rows and ACF stores these types of values in a serialized array in a single DB entry. You will need to convert the value.
My suggestion would be to create a new field name for ACF, but how you proceed from there depends on what type of field you set up in ACF. What is the field type of the field you’re trying to use?
