You may use Bulk Product Edit (BPE) to edit the standard product type of a product you sell, and the feature is available either by bulk edit or CSV edit.
Step 1: Find the ID number for standard product type
In both ways supported by BPE, the first step is to find the ID number for the standard product type to which your product is categorized. At Shopify, a standard product type is called a Product Taxonomy; you can find a full list of all product taxonomies in the lookup table here.
Product taxonomies (standard product types) are listed in the lookup table in the [ID Number] - [Full Name] format; the full name is a list of product taxonomy names connected by ">", where a parent category is followed by a child category.
A line in the lookup table showing one product taxonomy.
The product taxonomy name after the last ">" in its full name is the actual name of the product taxonomy listed on the line. In the list record above, the ID number for the product taxonomy is 61, and the name is "Pet Bed Accessories". It is a child category of the taxonomy "Pet Supplies", whose parent category is "Animal & Pet Supplies". This is equivalent to selecting the taxonomy in the following steps in Shopify Admin:
To find the product taxonomy you need in the lookup table, you need to use the search tool with your browser. In most mainstream browsers, the search tool can be triggered by the shortcut Command + F (on Mac), or Ctrl + F (on Windows PC).
Step 2 (Bulk edit)
To bulk-edit standard product types manually in the app, select Bulk Product Edit in the homepage and navigate to the Product Type page.
Accessing the Product Type page via the left side menu.
In "Step 3: Choose how to edit selected products/variants", choose the option "update standard product type", and then input the ID number of the product type you wish to update your products to.
The interface to edit standard product type in the app.
To bulk-delete standard product types of products, simply leave the input box blank.
Step 2 (CSV edit)
To automatically bulk-edit standard product types from imported CSV files, prepare the CSV file such that one column contains the ID numbers of the standard product types.
Preview of the standard product type column of a CSV file prepared for BPE bulk edit.
(The table header with content "Standard Product Type" is not required.)
In the BPE app, select Bulk Product Edit in the homepage and navigate to the CSV Import page.
Accessing the CSV Import page via the left side menu.
After uploading and previewing your prepared CSV file, scroll to "Step 4: Column for searching and column for editing". Include the column in the CSV file that contains the ID numbers for standard product types, and select "Product Standard Product Type" in the "To Update" selector.
The interface for column selection to update standard product type.
An empty cell on the Standard Product Type column will delete the existing standard product type for the product searched from the row in the CSV file.