Why do you want two meters to feed a single panel? That would defeat the (presumed) purpose of separate meters, eg seperable billing. One panel and meter for the house and one for the ADU. Simple and relatively cheap.

PG&E (service provider) said they can have only one line going to the property. So I am presuming, I need a panel or maybe two panels that will split this line into two one for the main house and another for ADU. I am no expert so please excuse my ignorance. What should the wiring and panel look like?

This link is to a 400 amp panel with two 200 amp meter connections, is this what I need: https://www.radwell.com/Shop?source=GoogleShopping&IgnoreRedirect=true&ItemSingleId=35550372&utm_source=google&utm_medium=cpc&adpos=&scid=scplp35550372&sc_intid=35550372&gad=1&gclid=CjwKCAjwivemBhBhEiwAJxNWN01DcnGw4Xm3uACbuiiGXRClzlUEXoLIB2xD5G4GAWicTlyzr5eQ0RoCk4YQAvD_BwE

I'm not an electrician, but that looks like it would do what you want. In our part of the country it is more typical for the meter bases to be separate, on the outside of the house and the breaker panels to be inside rather than an integrated unit. The POCO drop can feed more than one meter. Your electrician should be able to sort this out easily; get what they recommend.

My situation was just the reverse - I needed 400A so the builder put a single meter pan but ran two 200A lines to it and two 200A lines from the meter pan to two separate load centers. I never was able to see the meter pan box to see how they were wired.