Item number in Purchase order

In the purchase order template, i want to add in a column, the serial no or item number per line item, like 1 ,2 ,3 , or ex01, bd 200, … to identify with clients relevant item. Currently i dont see a column in my desktop version.
same is the case with Sales quotation, if we are able enter client ref per item.

pls help

please do not double post your questions.
you posted the same question in another topic.

also read the guides section and search the forum as these have been discussed many times.

https://guides.manager.io/10303
https://guides.manager.io/10411