When i want to add my gmail account to iOS mail app, it already has two old email accounts prepopulated. How do i delete those? I’ve tried deleting. Tried network reset, tried erase google history, made sure I’m signed out if any google accounts.

Add first the account that you want to add, see this Apple article:  Add an email account to your iPhone, iPad or iPod touch

Add an email account to your iPhone, iPad or iPod touch – Apple Support (UK)

Now remove the other 2 accounts:

Try this -> go to Settings -> Mail -> Accounts -> scroll & tap the email address you want to delete -> scroll down & tap Delete account.

Can you please help me delete couples old google accounts?.

Try this -> go to Settings -> Mail -> Accounts -> scroll & tap the email address you want to delete -> scroll down & tap Delete account.

The OLD accounts I want to delete are not on the ACCOUNTS listing. It's not until I click on ADD ACCOUNT that the huge list of accounts shows up. THAT is where I cannot delete the account(s).

Those are not accounts on your phone. They are accounts in gmail. You will have to delete them from the gmail website.

I'd like to know "where" I can find that list then, because this happens on my iPhone.

Are they your gmail accounts?

is this a 2nd hand phone that was not reset to factory before you got it?