Please can you explain more steps?

This is the screen that appears to me

https://ibb.co/YdCYyK4

Also, I do not want to zero the number

I want to convert some pieces

For example, if the stock is 5 I want to transfer only 2.

thanks

I'll try to give a bit more specific info and links that could help you.

The screenshot was helpful.. tx

When starting the inventory, also add the new product to your selection:

- go to operations > inventory adjustments > CREATE

- add both products to the selection

- start inventory

As a result you'll see all available stock, with the serial numbers.

(on your screenshot it seems you have no serial numbers and no stock at hand)

decrease the available stock of the old product

increase the available stock of the new product + enter the serial number

To increase:

- click on CREATE to create a new inventory line

- select the new product

- select location

- enter '1' as quantity

- enter the serial number

When all lines have been added and the stock of the old product has been put on zero, click VALIDATE INVENTORY. This will generate the product moves.

This is a useful link: https://www.odoo.com/documentation/user/14.0/inventory/overview/process/initial_stock.html?highlight=inventory adjustments