Hi Rachana,

First of all, I assume you mean a list of objects and the values of a specific attribute in those objects. One attribute does not contain multiple values.

In this case, You can use a Retrieve activity . A Retrieve activity can be used to get one or more objects, either by directly traversing an association of another object, or by retrieving objects from the database.
refer https://docs.mendix.com/refguide/retrieve/

And you want to perform particular action on those objects then use list operation
Refer https://docs.mendix.com/refguide/list-operation/

Thanks,
zia