Need to change "child" number as the prder number is different

Yehonatan_td83vp

i have the main project line number lets say SO000234
and i want the child auto numbered will be SP0001,SP0002....

John Funk

Hi Yehonatan - Welcome to the Atlassian Community!

If you are talking about the key (or ID) of the issues, that is not possible and you have no control over how those are populated. The key of the issue will be the project - sequential number. You have cannot change that.