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

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


write record


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

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


write record


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

I have a column named req number where value is generated automatically in database whenever  a form is being submitted .

So when the task goes to supervisor i want to display the req number value from database in read only mode to supervisor 

you can use grid layout and set that field in read only mode. Editable Grid Component - Appian 22.4

this is still to view information to really provide a valid answer,
Do you have UI restrictions?
What CDT/Record are you using? 
How is your process built?