US healthcare advice needed for a visitor

Hello!

I am from an European country and about to leave for a 1 year intern project in the US

I need some advice on the medical point of view.

I am on therapy for PCOS (hormonal issue) with hormones (birth control) and metformin (insulin resistance medicine). It's not a life threatening condition but I would not be well if I had to stop the treatments.

I am trying to understand how to proceed, cause my home country won't provide medicines 1 year in advance, the medical insurance base program given by the program agency will not cover anything pre-existing, the upgraded plan only "acute pre-existing conditions"(what does that mean ?) but it's also a monthly added expense, so I need to understand what other options are there

Are walk in clinics going to prescribe these medications given that I already have my country's Doctor 's prescription?

I know walk INS are anything between 100-400, are they also gonna ask for bloodworks if I already have all bloodworks with me?

Please if you have any advice it's so welcome!