//First query all DashboardDolder in the org.
Map<Id,Folder> folderMap = new Map<Id,Folder>([SELECT 	Id,
							DeveloperName,
							NameSpacePrefix
							FROM Folder
							WHERE
							Type = 'Dashboard']);

//Query all Dashboards in the system.
List<Dashboard> dashboardList = [SELECT FolderId,
			          DeveloperName,
			          NameSpacePrefix
			          FROM Dashboard
			          USING SCOPE everything];

List<String> DashboardNames = new List<String>();

for(Dashboard DashboardObj: dashboardList){
	String DashboardName;
	//If a Dashboard is inside the folder then we should get the folder name also.
	//If Dashboard is in public folders then we should prefix with "unfiled$public"
	//We should also check for Managed package Dashboards. If namspace is not blank then prepend foldername and dashboardname followed
	//by '__'

	if(folderMap.containsKey(DashboardObj.FolderId)){
		if(String.isNotBlank(folderMap.get(DashboardObj.FolderId).NameSpacePrefix)){
			DashboardName = folderMap.get(DashboardObj.FolderId).NameSpacePrefix + '__' + folderMap.get(DashboardObj.FolderId).DeveloperName;
		}else{
			DashboardName = folderMap.get(DashboardObj.FolderId).DeveloperName;
		}

		if(String.isNotBlank(DashboardObj.NameSpacePrefix)){
			DashboardName = DashboardName + '/' + DashboardObj.NameSpacePrefix + '__' + DashboardObj.DeveloperName;
		}else{
			DashboardName = DashboardName + '/' + DashboardObj.DeveloperName;
		}

		DashboardNames.add(DashboardName);
	}else{
		if(String.isNotBlank(DashboardObj.NameSpacePrefix)){
			DashboardName = 'unfiled$public/' + DashboardObj.NameSpacePrefix + '__' + DashboardObj.DeveloperName;
		}else{
			DashboardName = 'unfiled$public/' + DashboardObj.DeveloperName;
		}

		DashboardNames.add(DashboardName);
	}

}

System.debug(JSON.serialize(DashboardNames));
//Once all Dashboard names are printed, we can prepare package file and retrieve Dashboards from Org.