Pdf creation (PO) does not get value out of PO series

[sternbj]

Thank you so much for your help! I just printed the wrong field. So I edited a field that was not shown.
Such easy solution.

If I get also good answer to my other question, that would be so nice. It should also be very easy to answer.

How do I get a value of other doytype

For some reason, the quotation number of the supplier quotation is not linked to the purchase order. It makes in my view sense to put this value into the print format of the PO. How can I create a field that gets from the linked supplier quotation the quotation number? I tried with a link field, but I only managed to get the different supplier quotations as options not the quotation number. I would be very thankful for any help