How do you know what kind of oxygen sensor needed for a 1994 940 Volvo 4-cylinder non turbo?

I just bought this exact vehicle last week and ordered a Beck/Arnley oxygen sensor on eBay for $20 bucks.

Bosch may be the best brand sensor (also called O2 sensor) but you'll be paying a lot more. NGK is another brand. My 940 will not be getting many miles per year, so I went cheaper.