"Warning! Autoincrement field should be a Primary Key" - This message implies that Primary Key is needed for this field.
Example: As we can see "ID" field provokes the following warning: "Warning! Autoincrement field should be a Primary Key".
Look at the Indexes. Check Primary Key index if there is such an index in your table. This will resolve the problem.
In case there is no Primary Key for this field we recommend you to create the index in your source database to make the conversion 100% successful. In case you won't pay attention to this warning and run the conversion without creating Primary Key, Autoincrement won't be set to this field.
