Importing images that already exist on your server is exactly the same as importing images from a URL, except you only need to specify the file name of the image.
The images you are importing must be uploaded to /wp-content/uploads/
You can preview Image as per below screensort.
The images in this folder will be copied to the paths used by your WordPress Media Library when the import is run – typically, /wp-content/uploads/YYYY/MM/.