This bit tells you how many \ are in the string:
=LEN(A19)-LEN(SUBSTITUTE(A19,"\",""))

So the formula simplifies to:
=MID(A19,FIND("*",SUBSTITUTE(A19,"\","*",2))+1,LEN(A19))

This bit replaces the second \ with an *
=SUBSTITUTE(A19,"\","*",2)

Finally, the MID function looks for the ONLY * in the string and returns the characters from that position PLUS 1, to the end of the string.
=MID(A19,FIND("*",A19)+1,LEN(A19))