Hello aisha,

You can give sequence on menus through code by simply adding sequence attribute on that particular menu in xml file where usually menuitem is defined. The higher sequence number will set that menu downer accordingly. Default sequence will be set to 10 for any menu. For example,

<menuitem id="menuitem_id" name="Position/Of/The/Menu/Item/In/The/Tree" action="action_id" icon="NAME_FROM_LIST" groups="groupname" sequence="<integer>"/>

example-

    <menuitem id="menu_fleet_reporting_costs"
              parent="menu_fleet_reporting"
              action="action_fleet_reporting_costs"
              sequence="1"
              groups="group_fleet_manager"/>

Note - Menu items with the same sequence numbers are sorted by order of creation (_order = "sequence,id").

And yeah after updating xml file, Don't forget to update that module to apply changes.

For more details, You can go through doc link

Hope this will help you.