This is for certain people do not wish to upgrade to Office365 Group.
Column EXT:
=RIGHT(A2,LEN(A2)-SEARCH(".",A2)+1)
Column LTD:
=IFERROR(RIGHT(RIGHT(B2,LEN(B2)-SEARCH(".",B2)),LEN(RIGHT(B2,LEN(B2)-SEARCH(".",B2)))-SEARCH(".",RIGHT(B2,LEN(B2)-SEARCH(".",B2)))+1),RIGHT(B2,LEN(B2)-SEARCH(".",B2)+1))