I've purchased a 3/8 oz. hula popper and I need to know what size hooks to replace it with

You can see the stock hook sizes here:

 

http://www.basspro.com/Arbogast-Hula-Popper/product/15534/

I generally just eyeball it. You don't want the two hooks to catch each other. You can go up one size usually if go with a short shank hook. My personal favorite replacement hook is Owner ST-36. VMC Vanadium Inline hooks are a good choice too.

I generally just eyeball it. You don't want the two hooks to catch each other. You can go up one size usually if go with a short shank hook. My personal favorite replacement hook is Owner ST-36. VMC Vanadium Inline hooks are a good choice too.

I agree.........I do like to use a 3x.