Warehouse permitted under CE,Rule 4(4)

we are having 2 plants & one warehouse permitted under rule 4(4) for both the plants in same state.Goods are cleared for storage from plants without paying duty. Export & domestic sale is made from warehouse on paying applicable duty . Now we have migrated for single GSTN for both the plants and warehouse. We want to know the exact documents procedure for transfer of goods from plants to warehouse under GST.