What Plugin goes "type" of a FieldStorageConfig type? I have a module creating a field type. It works.  I can create and add the field through the admin UI.  However, I am trying to update a content type with hook_update_N and change a field from entity reference to my field type. I am creating the FieldConfig and FieldStorageConfig like this

$field_storage = FieldStorageConfig::create([
       'field_name' =&gt; 'content_category',
       'entity_type' =&gt; 'node',
       'type' =&gt; 'my_field_type',
    ]);

$field = FieldConfig::create([
      'field_storage' =&gt; $field_storage,
      'field_name' =&gt; 'content_category',
      'bundle' =&gt; 'story',
      'label' =&gt; $label,
      'settings' =&gt; array('display_summary' =&gt; TRUE),
      'entity_type' =&gt; 'node',
    ]);
    $field-&gt;save();


This results in an error that says

The "my_field_type" plugin does not exist


but i can  create a field of type "my_field_type" and when I export configurations for my field created through the UI  the type says "my_field_type"

So What plugin is it looking for in the "type" field of a fieldConfigStorage?  In my Plugin folder of my module the Formatter.php  Field.php and Widget.php  which of these is the correct one?
My Bug was actually in 

entitity_get_form_display()-&gt;setComponent('field', array(
type=&gt;my_field_type))


it should have been

entitity_get_form_display()-&gt;setComponent('field', array(
type=&gt;my_field_type_widget))