Hi

This is a process you can use to change product type. I got it from Thuy Ngoc, so all credits to him.

Step 1: Go to menu Settings => Technical => Actions => Server Actions.
Step 2: Create an action with the following information:
+ Name: Update product type
+ Model: Server Action
+ Action To Do: Execute Python Code
+ Python Code: env.cr.execute("""Update product_template set detailed_type = 'consu' where id = id_of_product_template """)
Step 3: Click Run

To get the ID of your product, make an export with that field. Replace "id_of_product_template" in the code with your specific number.

If you want the change product type to storable product, replace "consu" with "product".

hi Stefan,

the answer you received from Rakesh is good and easy.
I f you also need to sum the sell statistics, you can try to manage them by labels on that products. Another possibility is to export all data of consumabile item, and import them in the storable one, but export/import is always more complicated option

Below is a refined code for the above. Execute it as server action. Remember the product need to be of type 'consu' if you're in odoo18 
# Update both type and is_storable
env.cr.execute("""
    UPDATE product_template 
    SET is_storable = true
    WHERE type = 'consu'
""")

updated_count = env.cr.rowcount
env.cr.commit()

# Show notification
action = {
    'type': 'ir.actions.client',
    'tag': 'display_notification',
    'params': {
        'title': 'Update Complete',
        'message': f'Updated {updated_count} products type and storable status',
        'type': 'success',
        'sticky': False,
    }
}

From database edit tables product template field type