How to remove milestone in

i am using and i am new in gitlab,
i have many projects in and i create may milestone also,

but all milestone is created under oldproject and i oldproject is deleted since i cannot find the remove button for milestone i have created.

currently oldproject is deleted but all testing milestone is still there,
so how to remove all the milestone, i still can not find the way to do this.

Maybe you could use the API for that. There is a method to delete milestones from projects