You need use openssl to make pem.
node 8555
openssl rsa -in private_full_node.key -out pkey.pem
openssl x509 -in private_full_node.crt -out pcrt.pem
wallet 9256
openssl rsa -in private_wallet.key -out pkey.pem
openssl x509 -in private_wallet.crt -out pcrt.pem
light wallet 9257
openssl rsa -in private_full_node.key -out pkey.pem
openssl x509 -in private_full_node.crt -out pcrt.pem