Trying to make a formula/rule to assign a county to a region in separate columns

Good morning,

I am trying to make a spreadsheet. My employer primarily works in "regions" within our state, but it's still important to know the county. I have about 500 facilities I need to list, and I want to region of the state for the facility listed in one column and the county in the next column. Is there a way to make this an automatic thing? We have 120 counties in our state and each region has assigned counties, so I feel like I could make a formula (?) to just write the county and it assign tona region? Does that make sense? But I don't know how to make it happen.

Thanks in advance.