Copy and paste the following commands in order:

termux-setup-storage (accept when prompted)

termux-change-repo

pkg update

pkg update && pkg upgrade

pkg install wget

wget -L https://raw.githubusercontent.com/Pipetto-crypto/mame/termux-chdman/chdman.sh

source chdman.sh

Everytime you need to convert your games paste the last command and answer the questions.