Hi Ather,
Filling the dropdown is not a problem in this case.
The page you are editing probably contains a dataview with object type ‘MyFirstModule.drop’ coming from a context datasource.
If you use this page from a navigation profile, using dataviews with datasource ‘Context’ is not possible. You need to use another datasource type. For example a Datasource Microflow that returns an object of type ‘MyFirstModule.drop’.
If you show this page using a Microflow with activity 'Show page’, you have to send an object of type ‘MyFirstModule.drop’ to the page in this Microflow.
More information can be found here: https://docs.mendix.com/studio/page-parameter/ and here: https://docs.mendix.com/refguide/data-view/
Hope this helps!