消滅 しょうめつ可能 かのう せい都市 としであれば
shōmetsukano useito shideareba

Noun
Da Copula

The "-eba" conditional form ("if/when…") of 消滅可能性都市

1. If it were a city with a possibility of annihilation; If it were an annihilatable city

Ba Conditional