» Separtaing A String Into Substrings.

Problem:

Separating the string in A2 into 3-letter substrings.

Solution:

Using the MID and ROW functions, as follows:
=MID($A$2,(ROW()-ROW($A$2)+1)*3-2,3)

Example:

Full String_____________Substrings
abcdefghijklmnopqr______abc
________________________def
________________________ghi
________________________jkl
________________________mno
________________________pqr

Screenshot // Separtaing A String Into Substrings.