HOW THE BOOKING REQUESTS CAN HAVE A UNIQUE REFERENCE NUMBER

Here is how to setup a unique ID in your form: https://support.jotform.com/help/79-How-to-Add-Custom-Unique-IDs-to-your-Form-Submissions 

Let us know if you need more help, we will be glad to assist you.

I am looking for something simulacra but want the field shown on the form

Example:

(Purchase Order #505)

Next time I fill out the form

(Purchase Order # 506)

That is possible to accomplish with the Unique ID widget, next time you fill the form, it will auto-increment.

Let us know if you need more help.