You can migrate Data directly from one Salesforce Org to another, without needing to download CSV Files.
Head over to the Jobs page and click on New Job. Fill in the Name, choose your Target Instance, Source Instance, and the Operation. The Target Instance is the Salesforce Org that you want to Import Data into, and the Source Org is where the Data should be coming from. Once you have filled in these fields you can click next.
Choose the source and the target Objects that you wish to Migrate. These do not have to be the same in each Org.
Here is where you tell Dataimporter which source data should be migrated. On the left you will see every standard and custom field listed, and beneath you will see all of the Lookup Relationships as well. On the right side, are all of the Target fields which you can select to make sure that they will be included in the Mapping. To ensure that all of the Relationships are moved across make sure you make the Lookup Relationships using a key that is available in both orgs.
To make sure you Migrate the Lookup Relationships with the records, select them as shown below:
Here, Dataimporter will select the Account.Name, and Owner.Name from the source records, and create lookup relationships in the new org, using the Account.Name and User.Name.
On the clean screen, you can create an SOQL filter, to select which records you want to migrate. If you want to migrate all records for this object, you can simply leave the filter field blank.
Preview the a sample of the records to be migrated. The SOQL Filters, and Deduplication Rules have been applied to the preview so you can check they are working correctly. Any formulas you have Mapped will also be evaluated, and appear on the Preview screen.