I worked in that department, but I don't know what that department does as a whole.
I was in that department, but I don't know the full scope of what they do.
一番目のI worked in that department, but I don't know what that department does as a whole.はちょっと直訳的な感じですが、自然に使えます。
as a wholeは「全体として」という意味です。
英語で仕事の話でfull scopeという表現を、全体像・やっていることや役割の全部の範囲という意味でよく使われていますので、
I was in that department, but I don't know the full scope of what they do.
でも使えますね。
At work I was in a certain department, but I only worked there for a short time, so I only know part of what they do. I don't know the full scope of what that department does.
仕事でとある部門にいましたが、いた期間は短かったので、いったい部署としてどういう仕事をしていたのか部分的しか知らず、全体は知らないと言いたいです。
ご参考になれば幸いです！
I was in that department but I don't know the full scope of the job.
"その部門にはいたけど仕事の全体像は分からない"
- I was in that department but I don't know the full scope of the job.
- I worked in that department but I don't know exactly what they do.
- I may have worked in that department but I don't know all of the details about the job.
アメリカ合衆国 
