merge folder and then delete source contents

So i have two folders with those folders I have folders and within those i have files.
desired:
-- takes folderA - source and merges it with folderB - destination (adding folder and files that are not in folderB - destination without deleting anything)
-- create folders that are in folderA - source that aren't in folderB - destination
-- then moves to trash folderA content upon success merge.
tried:
-- sync seems to take the contents of folderB - destination and removes the existing files seems more like a mirror sync rather than a merge sync
folderA - source
_________
-folderB1
-- file B1-3
-- file B2-4
-folderB2
-- file B2-3
-- file B2-4
-folderB3
-folderB4
folderB - destination
_________
-folderB1
-- file B1-1
-- file B2-2
-folderB2
-- file B2-1
-- file B2-2
-folderB3
Result:
folderA
_________
<empty>
-folderB1 - destination
-- file B1-1
-- file B2-2
-- file B1-3
-- file B2-4
-folderB2
-- file B2-1
-- file B2-2
-- file B2-3
-- file B2-4
-folderB3
-folderB4
desired:
-- takes folderA - source and merges it with folderB - destination (adding folder and files that are not in folderB - destination without deleting anything)
-- create folders that are in folderA - source that aren't in folderB - destination
-- then moves to trash folderA content upon success merge.
tried:
-- sync seems to take the contents of folderB - destination and removes the existing files seems more like a mirror sync rather than a merge sync
folderA - source
_________
-folderB1
-- file B1-3
-- file B2-4
-folderB2
-- file B2-3
-- file B2-4
-folderB3
-folderB4
folderB - destination
_________
-folderB1
-- file B1-1
-- file B2-2
-folderB2
-- file B2-1
-- file B2-2
-folderB3
Result:
folderA
_________
<empty>
-folderB1 - destination
-- file B1-1
-- file B2-2
-- file B1-3
-- file B2-4
-folderB2
-- file B2-1
-- file B2-2
-- file B2-3
-- file B2-4
-folderB3
-folderB4