That would depend on what version of ACF you’re using. If you’re using ACF4 (from the wordpress.org) then you’ll need to use a URL field, or with some work a text field.
If you’re using ACF5 which is currently only available here https://www.advancedcustomfields.com/pro/, then there are a couple of other options. The page link field in ACF5 has options not available in ACF4 and there is the new Link field type. For a complete list of field types in ACF5 see this https://www.advancedcustomfields.com/resources/.
