What size hook do I need?

[Meganrose2208]

I recently downloaded a pattern that said I needed a hook NO2 and No3. 
 

Does anyone know what size this is in mm? 

[Lilol]

I found a wiki page that lists the sizes. It shows (2) 2.75mm (3) 3.25 mm

https://en.wikipedia.org/wiki/List_of_United_States_standard_crochet_hook_and_knitting_needle_sizes

[Bailey4]

Are you crocheting with yarn or thread?

[Granny Square]

Just in case, here are steel hook sizes, which are normally for doily-size thread but there's some overlap in the bigger steel thread hooks and smaller yarn hooks (which are usually aluminum, plastic or sometimes wood).

https://www.craftyarncouncil.com/standards/steel-crochet-hook-crochet-thread-sizes

[Granny Square]

Forgot to add, on the link I gave you, there is a menu on the right hand side, if you click on 'standard yarn weight system' it tells you which hook size range are typically used for each US yarn weight class.