Loop in list and fill in other list

Hello to everybody
I really hope to help me. This will save me a lot of time each Mondays.
A little preliminary. First of all for security reason I deleted 99% from orginal file witch one is much complicated. It is normal. This is my solution to manage the purchse orders from main costumer.
Approximately we have 5000 orders per year. You can immagine we are exporting each week about 100 different PO's.
So, I want the quantity from "Invoice" automaticly to be filled in "Order" just with one click after export.
All the PO numbers like "P000003" are unique.
The yellow marked lines are exported orders.

Is it possible to do it and if yes, now?

Thanks you in advance!

P.S. I'mfrom east Europa.so I'm sorry for my not correct gramatically sentences.

Hi noboffinme
Thanks for attention on my problem.

The column with name "pieces" is quantity.
Attached updated.

Hi noboffinme

Few days I thougt how to describe my needs.
I'll try in simple words.
Genarally, I want VBA code.
What the code shoud do it?
To find quantity from one sheet and to write in another, according purchase order number.
The idea with Vlookup is OK, but immagine next export! The purchase order numbers are different and if I use Vlookup function the values in yellow rows will be delelted because it is formula.
That is why I need VBA.
Sorry, but it is difficult explanation to me even in my native language!