Mongoose include fields from a secondary document using $lookup
You need $lookup with custom pipeline to match against name or location field and then simply you can run $project to get desired format of your result documents:
db.Locations.aggregate([ { $lookup: { from: "Orders", let: { loc_id: "$_id" }, pipeline: [ { $match: { $expr: { $eq: [ "$$loc_id", "$_id" ] } } }, { $project: { _id: 0, products: 1 } } ], as: "orders" } }, { $match: { orders: { $ne: [] } } }, { $project: { _id: 1, name: 1, products: "$orders.products" } }])