Hello Arkadiusz Zimniak,
Can't you simply create a new item?
Renaming is not always a good option especially if subsequent reports/analyses depend on the item number, such as BI reports or other inventory reports that you have run.
If you would like to have a 'clean' and consistent system then creating a new item is always the better option even if there is bit more work related to this.
Best regards,
Ludwig