How to buy an used wheel, what size, what are the crucial numbers?

Hi everyone,
I have Aveo 1.2, year 2007, bought in Europe, Croatia.
Tires are 185/55/15. Wheels have 4 screws.
I have to buy a wheel, used. People in the ads usually write 15", 4x108 or 4x98 or 4x113 or else...
What is the proper size for my car. How can I tell when I have a wheel in front of me?
Thanks

your car is 4x100. 56.6 center bore, offset is determined by which wheel you have.

if you are just buying one replacement wheel, you need to get an exact match.

Thank you very much