https://en.m.wikipedia.org/wiki/Demographic_history_of_Bosnia_and_Herzegovina

I'm not from that area, so I got my numbers from the "1895 census" section, which mentions:

"The Catholic Encyclopedia treated the majority Slavic population (98%) as Serbs".

The census is also listing the numbers by religion, with around 43% Christian Orthodox, 37% Muslim and 20% Catholics ...