My Custom drupal 8 module does not shown in modules list
Remove the spaces between the identifiers and colons:

name: Drupal Center Custom Migrate
description: This module provides custom migration configuration and plugins to migrate my custom site from drupal 6.
type: module
core: 8.x

package: Custom migrate
dependencies:
  - migrate
  - migrate_plus
  - migrate_tools
  - migrate_upgrade
  - migrate_drupal


Then it'll work.

See the YAML rules for more info.