split flow into 2 with tMap by filters
filter for 1 - length(col) >= 3 and (left(col,3)).equals("abc")
filter for 2 - length(col) >=3 and (left(col,3)).equals("lmn")
flow 1 send to INSERT, flow 2 send to UPDATE
this is only example of logic, because You also can decide - what todo with other records? You can make double filter and send both to INSERT/UPDATE