Hi Harvey,
In this case you have three options
1.By changing PO : Change PO line item to 6000 and add new line item of 44000 with plant 2 ....in this case you have to release PO again.
2.Stock Transfer PO Process: Take Good receipt in Plant 1 and Create Stock Transfer PO with Supplying plant Plant 1 & Receving Plant 2.
3.Transfer Posting:Take Good receipt in Plant 1 and do transfer posting with movement type 301.
Regards,
