Both .brs and .papers files are used in Corel Painter software, so it might be very well possible that only this software is capable of brs to papers conversion - if it's even doable. Perhaps it's more of a workflow in which you use (or import) particular brush to Corel Painter and use it for making new paper texture file (.papers). In any case, if you have issues with these files or their import/export, it would be perhaps wise to contact Corel support.
Updated: March 15, 2023