Place chdman.exe in a folder where you keep your ROMs or games. For simplicity, create a folder on your desktop called CHD_Convert .
Open Command Prompt (Windows) or Terminal (Linux/macOS) in that folder. Run the following command: convert chd to iso
chdman extractdvd -i "input_file.chd" -o "output_file.iso" Place chdman
This is often found within MAME tool packages. convert chd to iso
for f in *.chd; do chdman extractdvd -i "$f" -o "$f%.chd.iso"; done