Location of WP-Pizza Menu Files

what do you mean “you are looking for the files ” ?
what are you expecting to find ?

I want to add the meal sizes. I Have about 54 and I do not want to add them one by one.

Menu Items i have 154 items

and so forth

you have to.
these are database entries.
there’s nothing for you to edit

i also assume you are talking about actual meals , not sizes per meal (as 54 per meal would be …well ,…strange

i.e. a meal can have different sizes (such as small,medium large….) and I assume you don’t have 54 different of these sizes…(but maybe I’m wrong on that one though)