To read response from SP.UserProfiles.PeopleManager/GetPropertiesFor in nintex workflow online

I want to fetch user profile properties for a user and I have set the URL which returns XML response. But I am unable to correctly set the Item Path in the Get Item from Dictionary action in Nintex workflow

Call web service action calls below URL:

site/_api/SP.UserProfiles.PeopleManager/GetPropertiesFor('i%3A0%23.f%7Cmembership%7Cusername%40domain.com')

Xml returned from the service call

<d:UserProfileProperties><d:element m:type="SP.KeyValue"><d:Key>FirstName</d:Key><d:Value>Vishal</d:Value><d:element></d:UserProfileProperties>

Item name or path I used but I guess this is incorrect. can anyone help ?

d/UserProfileProperties/element/Key==FirstName/Value

Thanks.