$a)$

$230=2.3\cdot {10}^2$

$b)$

$3600=3.6\cdot {10}^3$

$c)$

$18000=1.8\cdot {10}^4$

$d)$

$195000=1.95\cdot {10}^5$

$e)$

$120000=1.2\cdot {10}^5$

$f)$

$13400000=1.34\cdot {10}^7$