How to search within a document with stored ID?

I have this document:

{
    "_id" : ObjectId("5b774ebd88bff63a48a4019c"),
    "modelo" : ObjectId("5b774ebc88bff63a48a40198"),
    "tamano" : ObjectId("5b774ebc88bff63a48a40199"),
    "color" : ObjectId("5b774ebc88bff63a48a40196"),
    "terminado" : ObjectId("5b774ebc88bff63a48a40197"),
    "laserAlmacen" : ObjectId("5b774ebd88bff63a48a4019b"),
    "versionModelo" : ObjectId("5b774ebd88bff63a48a4019a"),
    "__v" : 0
}

And I would like to search within objects, for example within% "modelo" : ObjectId("5b774ebc88bff63a48a40198"),

If I make a populate() the modelo returns me:

{
    "_id" : ObjectId("5b774ebc88bff63a48a40198"),
    "modelo" : "4125",
    "__v" : 0
}

And I want to find all the documents that contain the same modelo.modelo .

I've tried with:

ModelosCompletos.find({'modelo.modelo': regex }, (err, resp)=>{
    //..Mas código...

})

But I do not get any results because it is not a nested document. I have been searching but I can not find how to solve this query.

I have thought of making two queries. The first one to search within the schema modelo and return the _id and then with this id search within ModelosCompletos but I would like to know if you can do everything in a single request.