This is the first baby that won't be using our old Britax infant carseat that snaps into the Britax stroller, so I'm confused!

Going to have a hand me down Chicco Keyfit infant car seat. I currently have a Britax single stroller, and a Baby Trend double stroller. Is there an adaptor I can get to fit the Chicco onto either strollers?

Or is it just easier for me to get the snap n go?