Hi @shalukumari - “abandoned checkouts” are how we refer to what some others may call “abandoned carts”. The /admin/api/2022-10/checkouts.json endpoint you provided is the correct one to query through REST.
You can confirm if the checkout is completed by looking at the completed_at field which would provide a timestamp of when the abandoned checkout has been paid for. If the checkout hasn’t been completed, it would have a null value rather than a timestamp. There is a bit more information here in an older post from one of my colleagues.
Hope this helps - please let us know if we can clarify anything on our end.