If you would like to apply a filter to the data that is migrated, you can do this via the Configuration --> Filters tab of your migration.
Select the object to filter
Choose from the dropdown the record type you wish to filter. You can add multiple filters as needed.
Select the field to filter by
Configure the filter from the available fields in the dropdown. For example, ID, name or even by a custom field value of your choice.
Validate the results
Run the sample to validate the results are as expected. If you need to make changes to your filter setup, or wish to remove the filters, you can do this by navigating back to the filter setup page. Please note - any changes to the filter (including removal) will require that you restart the migration to apply the changes.
Please note -
A record which is filtered out means that any related records will also be filtered out by default. For example, if the Account is excluded, then its related Contacts, Opportunities, Notes, Activities, etc. are also excluded.