Step 1: Install putty tools on Debian ubuntu sudo apt-get install putty-tools
Step 2: Convert ppk to pem using putty puttygen {ppkfilename}.ppk -O private-openssh -o {pemFileName}.pem
Step 3: change permission of pem file You need to change the permission of the file to 400 to use pem file. chmod 400 {pemFileName}.pem