Hello. My name is Eugenia. I am Ukrainian citizen, but live in USA 2,5 years and have a green card. I want to go to Ukraine to see my relatives. I am planning to be there 1 month. What kind of paperwork I need to do to go to Ukraine? Do I need visa? Is it still enough to have a green card to come back to USA?

Thank you very mach

For a short trip, you don't need any paperwork. Just show your GC to immigration officers when you enter US.