Need Expert in PHP and Angular

I'm looking for an expert PHP and Angular to custimize this script [login to view URL] We are a library and we sell paper products, for example paper in the form of photocopying documents or selling paper in a carton or in a package or in paper and we want this sale to be linked to the Quantity of paper purchased for sale in the library Selling in a Packs that consists of 100 papers, or by selling in carton which consists of 5 Packs, and each Packs consists of 100 Papers and the total will be: 5 Packs * 100 Papers = 500 Papers. The quantities of units are distributed as follows: - Item table of Product (A) Carton = 5 Packs = 500 Papers - Product (B) Pack = 100 Papers - Product (C) Paper = 1 Paper * With full quantity control A + B + C with several barcodes for each type and for All only one quantity. For example: --------------------- We bought 10 Paper Cartons That mean in our stock 10 Paper Cartons Mean the Total= 10 Cartons * 5 Packs = 50 Packs * 100 Papers = 5000 Papers * Then we have 10 Cartons in our stock which equals 5000 Papers - If we sell ONE Paper, it becomes in our stock = 4999 Papers - If we sell ONE Pack, it becomes in our stock = 4900 Papers - If we sell ONE Carton, it becomes in our stock = 4500 Papers * For clarification, we will need from the developer to clarify the files that have been modified and all the additions that have been made, whether adding code or adding table into the database to transfer it to another files.