Can someone help me how to find how many times Paul mentioned repentance in regards to salvation for unbelievers? Thank you.
Try "repent WITHIN {Speaker <Person Paul>}"
His usage in his letters seems to be more focused on believers
The best is for you to go to a passage in Paul that mentions repentance (e.g., Rom 2:5). Then explore the context menu for all the searches you can do based on repentance (as lemma, as preaching theme, as theological topic, etc.).
For instance, I found more instances than the search above using "theological topic" as search route. However, there are hits in Graham's search that did not show in my results. So these searches can be complementary.
Thanks y'all.