Price per piece

Hi all,

I’d like to change service price from kg to piece.

I create trade agreements with price per pieces but If I’m going to create new sales order I can’t apply there price per piece because unit “pcs” is not convertible. I can use only units which system can convert from kg.

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In column “all” there are many of units but I’m not able to use them.

Have you some ideas if it is possible to change it?