How to get the IM details(what is the effort estimated and actual effort..etc) through command line

It depends. Are you trying to retrieve existing field values or create a computed field? Is this a CLI or API script? Or is it a trigger?

To get a specific field value for an item, e.g. "Overall Hours Estimation":

           im issues --fields="Overall Hours Estimation" [item ID]

If you are creating a computed field:

For a field computation that adds other fields, just use "Field1" + "Field2" + "Field3" and so on. You can wrap this in the isEmpty() function to ensure no errors. So isEmpty("Field1" + "Field2" + "Field3",0).

If you want to aggregate from other items, there's a couple different options.

To count up all values of a field for items in a relationship field, use the aggregate function.

For example, to add all "Hours Estimation" for software artifacts linked through the "Project For" field: 

aggregate("Project For", sum("Hours Estimation"))

To count up all values of a field for items matching a query, use the Query or QueryCorrelated functions,

For example, if you want to add up "Estimated Effort" for all documents that have the same project field:

query("administrator:Active Documents", Project, sum("Estimated Effort"))

Note: documentation on computed expressions, including all functions, can be found in the online help, under Server Administration > Calculations in Fields Charts and Reports > Computed Expression Function Classes