How to get a list of Process models Id in an application?

Not programatically. What do you try to achieve?

hi umarm7858  there are no inbuilt functions to achieve your requirement, AFAIK you may not achieve via code

You can get it through a report. Create an 'All Process Models' report. In that report, add a process model ID column with the definition "pm!id"

But that returns ALL models. Not just the models in a given application.

you have to check manually i guess

Please explain your use case for us to understand what you are trying to achieve and provide a reasonable solution.

Hi, umarm7858 , 
Agree to what Yogi Patel  mentioned, 
In addition to that, 
Just go onto the Process Report, click on magnifier icon at the end for applying filter.(as highlighted in the yellow color), 
Then you can see the text box below to type the Application Prefix (as highlighted in the green color). 
Another way is to use this report in a!queryProcessAnalytics and use that to fetch data on UI. (apply filters)
 

Note- Here is a consideration, that your application's prefix is used in PM name. 

Beware that it can also fetch the PMs which have this prefix in their name as mentioned by Stefan.
If that's the case, you need to apply additional text filtration over the field to only get the names which start with your Prefix, and ignore the ones which have prefix in between the name. 

For this to work, you need to apply some first level of filter inside a!query() of aa!queryProcessAnalytics() which is used in your UI, and an additional ER to filter this data to get the names of PM, only starting with the prefix.
I haven't tried out the UI method, but you can try and let us know if that works. 

Hope this helps.  

Export the application and refer to the export log to extract the Process Model ID or UUID.

Actually i want to clear the version history of each process model.I found a plugin which takes PM ID and delete the previous versions of it . Now i want to design a process model that should clear all process model version one by one using loop.

Thanks, although i made some adjustment but it worked well.