Hi, i wish to design an HMI for saponification plant, i need some elaboration

[nyame]

Hi, Scope of the project is, i need to design an HMI that control a saponification plant. now the key function of the HMI is, it enable the operator to inputs the quantity of product he needs in a tank. for example if he requires 1000 gallons of water he will input the values in the HMI and press enter once the tank get 1000 gallons it will switch off automatically.

the issue now is, the original file of the PLC is missing. so no documentation, but the wiring plan is there.

i uploaded the file am using from the PLC. looking at it, i noticed real world outputs in ladder 5. but most of the inputs, registers were used. when i look at the input data file i see some inputs on but i cant locate them on the ladder diagrams.

now the help i need is , how to locate the real world inputs on the ladder logic diagrams !

how to identify instructions that were used in the ladder diagram to the HMI to enable the operator perform those functions !