How to display data from database in interface in read only mode

Did you consider to display that value in a richtextDisplayField or a textfield with readOnly set to true? You have the associate developer certification. This is covered in the trainings and tutorials.

The requirement itself doesn't sound that complicated.
Basically that you try to show the primary key.
Or are you talking about to get the Id from the used node back to the process ? (and then into the form?)
if you write a record or cdt you can return the written result into the process variable by defining it as target at the "outputs" settings

Write to data store Entity


but its wild guessing
So, are we missing information here?