[Fix] Due to incorrect conversion factor user not able to make purchase return entry (#15163)

diff --git a/erpnext/controllers/sales_and_purchase_return.py b/erpnext/controllers/sales_and_purchase_return.py
index 62295d4..5e95b9e 100644
--- a/erpnext/controllers/sales_and_purchase_return.py
+++ b/erpnext/controllers/sales_and_purchase_return.py
@@ -151,6 +151,7 @@
 		"rejected_qty": 0,
 		"received_qty": 0,
 		"serial_no": [],
+		"conversion_factor": ref_item_row.get("conversion_factor", 1),
 		"batch_no": []
 	}))
 	item_dict = valid_items[ref_item_row.item_code]