[{"attributes":[{basicDetails:[{valueString:"valueString 1"},{valueString:"valueString 2"}]}]}]

db.collection.update({},[{$set:{"address":{$getField:{input:{$arrayElemAt:[{$getField:{input:{$arrayElemAt:["$attributes",0]},field:"basicDetails"}},1]},field:"valueString"}}}}],{multi:true})