How to make automatic item code

hello,

when making new item how to make the item field auto? and if auto, is there any formula that we can make of how the auto coding work? thank u

Yes you can use naming series to define automatic codes.
Refer :
https://docs.erpnext.com/docs/v13/user/manual/en/setting-up/settings/naming-series

Hi @Yudi_Firmansyah,

Adding in @Rahul-R’s answer, Please also check in Stock Setting.

After saving the Stock Setting, Please reload and check it.
Thank You!