How to convert a multi-file open api 2.0 definition to 3.0 spec definition without changing the file structure

Question

I have multi-file open api 2.0 definition, main file is called main_openapi.yaml that contains the top level fields and further details are in separate files. I want to convert this definition to 3.0 spec definition without changing the folder structure or combining them in to one yaml file.

Below are the details of my spec:

swagger: "2.0"
info:
  title: Sample API
  description: API description in Markdown.
  version: 1.0.0
host: api.example.com
basePath: /v1
schemes:
  - https
tags:
  - name: user
    description: Operations about user
  - name: health
    description: Operations about health

paths:
  /users:
    $ref: './user/userCreate.yaml'
  /users/{userId}:
    $ref: './user/userUpdate.yaml'
  /users/list:
    $ref: './user/userList.yaml'

  /groups:
    $ref: './group/groupCreate.yaml'
  /groups/{groupId}:
    $ref: './group/groupUpdate.yaml'
  /groups/list:
    $ref: './group/groupList.yaml'

  /locations:
    $ref: './location/locationCreate.yaml'
  /locations/{locationId}:
    $ref: './location/locationUpdate.yaml'
  /locations/list:
    $ref: './location/locationList.yaml'

Tried

1. openapi-generator-cli generate -c config.json tried with a conf file as shown below:

{
  "openapi-version": "3.0.0",
  "info": {
    "title": "OpenAPI Specification 2.0 YAML File Conversion",
    "version": "1.0.0"
  },
  "generator": "openapi-generator-cli",
  "config": {
    "input-files": [
      "specs/main_openapi.yaml"
    ],
    "output-format": "yaml",
    "output-file": "openapi_gen.yaml",
    "preserve-file-structure": true,
    "preserve-refs": true
  }
}

getting this error :

Unable to query repository, because of: "Request failed with status code 504"

Response:
date Tue, 13 Jun 2023 15:59:58 GMT
content-type text/html
content-length 160
connection close
server nginx

2. redoc-cli bundle -o output.yaml input.yaml -> convert using swagger editor online -> redoc-cli split -o output-folder input.yaml

The file structure is not preserved