Go to Sales > Configuration > Settings and enable Units of Measure & Packagings.

Hi,

In the Odoo Online Edition, you are running with the Odoo18.2 Release, which has been removed while 18.1 was released.


You can find it in the Odoo Official release of 18.1 (Inside the Inventory App Section), and for more, refer to the link below. 

https://www.odoo.com/odoo-18-1-release-notes


Thanks & Regards,
Sunny Sheth (shethsunny555@gmail.com)