Comparing images in different spaces

I want to check what indexes from a transformed harvard atlas ( correspond to regions associated with working memory ( The wm image is in mni space while the atlas is anatomically aligned, and I don’t know how to compare one with the other.

As background, the transformed atlas was used to generate dti connectivity matrices and I want to narrow them down to regions associated with wm, however I don’t have time to count the matrices again which is why I’m trying to just find the atlas index numbers (I’m writing my bachelor’s thesis and need to send it for checking soon).

Thanks for any help!