This is text.txt
SELECT *
  FROM zahtjevi
 WHERE datum_unosa BETWEEN SYSDATE - 3 / 24 AND SYSDATE; -- the last line in test.txt

This is test1.txt
SELECT SYSDATE,
       cnt cnt_zahtjeva,
       ROUND (cnt / (SYSDATE - min_datum_unosa), 1) avg_dnevno
  FROM test; -- the last line in test1.txt

@echo off
set LASTLINE=
setlocal enabledelayedexpansion
for %%a in (*.txt) do (
echo %%a
for /f "delims=" %%s in (%%a) do set LASTLINE=%%s
call echo !LASTLINE!
)

M:\>last_line
test.txt
 WHERE datum_unosa BETWEEN SYSDATE - 3 / 24 AND SYSDATE; -- the last line in test.txt
test1.txt
  FROM test; -- the last line in test1.txt

M:\>