Ensure the file is unzipped. If it is in a .zip or .7z format, PCSX2 may not see it.
, you would need a PS2 console from that specific region and manufacturing run. Dumping from your Console : You can use a tool like BIOS Dumper Pcsx2 Bios Usa V2.30 Download
Note: You may only have the .bin file. That is fine; PCSX2 will generate the others. Ensure the file is unzipped