Source movies with different aspect ratios

Hello,

I just started using the latest version of Premiere. The last version I used was from 2014, so it's quite different. Anyway, I'm building an anthology movie made up of short movies from different directors. Most of the movies look letterboxed in 16:9 but two of them have images that are a little bit bigger. I need all of them to be the same, so I was wondering how I might alter the two movies that are different so that their letterboxing looks the same (i.e., normal) as the others.

Thanks!