Are you trying to reuse ids from your source org into the target org? This is not possible as they are attaches to one org. Create a custom field on target org declared as an external id. Populate this field with the source id and use it as the search key for the upsert operation.
Yes, I do have external id's in target org with legacy id's. I want to know the steps on what components and how will I create a job for this scenario.
