Excel formula: how do i put a sum of the true concatenation outputs at the end of the string

I'm trying to put a number(the sum of the true concatenations) at the end of my string in excel.

I'm using if statements with concatenate:

=CONCATENATE("";IF(AG$1=31;"LETTERXX, ";"");IF(AG$2=CALENDER!$K$31;"SMS xxxx xxxxxx, ";""))

the output now is:

LETTERXX, SMS xxxx xxxxx,

and the output I want is:

LETTERXX, SMS xxxx xxxxx, 2

can someone please help me with this?

I would be really happy.