How to reorder the test case number when skipped upon deleting

I'm not sure but I think you're asking about the automatic test case ID that is applied when you create a test case.  There's no function to re-seed the next number used or to re-number all test case IDs.  You could potentially workaround the issue by creating a custom field and applying your own reference in there.

But if you're asking about how to re-order the position of a test case you can do that within the test cycle, going to the test cases tab and manually dragging test cases into the desired position.