Tom was using wire of the following thicknesses .33 mm, .275 mm, .25 mm, and .3 mm for some electrical work. order the wire from thickest to thinnest

We write the fractions divided into tenths , hundredths and thousandths . Decimal fraction is greater the greater the number nearest decimal place .
0,33 mm = 0,3 + 0,3mm
0,265mm = 0,2mm + 0,06mm + 0,005mm
0,25 mm = 0,2mm + 0,05mm
0,3 mm = 0,3

The largest number will be the highest digit decimal fraction
We have two numbers with the same value on the decimal place
0,33mm ,0,3mm

0,33mm > 0,3mm
(0,3 + 0,03)mm   > 0,3mm

the first two numbers  : 0,33mm , 0,3mm

The other two numbers are number two on the tenth place . So we check , which has a larger number of hundreds 
0,275mm > 0,25
(0,2 + 0,075)mm > (0,2 + 0,05)mm
0,075mm > 0,05mm

Answer : 0,33mm, 0,3mm, 0,275mm, 0,25mm