we have a list with list items as 20180101,20180101.01,20180101.02.
Now I need to create two different lists as parent child hierarchy from existing list.
If ".01" is there at right hand side(20180101.01) then it should reflect as "Branch1", If ".02" is there at right hand side(20180101.02) then it should reflect as "Branch2" else it should reflect "core branch".
20180101 should be parent and 20180101,20180101.01,20180101.02 should come as core branch, branch1, branch2 as child under 20180101.
why two different list and not just one list with two items branch 1 and branch 2 ?
In any case you need to create a module with your original list. In there you can create the mapping necessary to create update the parent of the current list. You need a line item call "parent code" where you'll put the last two characters. Save a view. Import from this view mapping the parent code to "Parent" and it will re-allocate the items.