"If you had a car, you would have been gone"
Translation:Ungalikuwa na gari ungalienda
"kuwa na", to have. You know how it conjugates in present tense (nina, una etc), but here's the past tense conjugations:
From there, just apply the conditional past rules to turn "ulikuwa na gari" -- you had a car, into "ungalikuwa na gari" if you had a car.