Got Letter In Mail Requiring Me to Get a PCP in 3 Days (NY)

I’m 22 and just got my first big job (WFH). My parent had Medicaid for us both and I no longer apply for that, so I had to get other insurance. I aged out of my pediatrician awhile ago and due to COVID I haven’t really made any appointments as nothings been wrong so I haven’t gotten a new PCP or anything (and my parent couldn’t take off to take me, and none of my friends or anyone I know are able to take me). I also don’t have a car yet as we couldn’t afford one for me and I only just got the ability to finally save for one with this new job. I’m not really sure what to do. I was waiting to have transportation (we live in the country so nothings nearby without a vehicle) to be able to schedule an appointment and find a doctor (as no one around me is open on the weekend and if they are they aren’t taking new patients) and now I’m stressed because this letter says I have 3 business days to find one. I had no idea this was a thing as I’ve never had to deal with insurance on my own before. Do I really have to? What happens if I don’t? Please advise.