Hey there @PsyKuKiller! Welcome back to the community! I don’t believe there is a method to get the actual hardware DPI of the mouse. The actual DPI of a mouse is hardware-based, and there’s usually no way for an application to read it directly unless it’s a mouse with specific software driver support.
An approach that might be viable is measuring the effective DPI, though this won’t be 100% accurate, it will give you a baseline for your own system.