AWS Load Balancer upload private key from JKS file

I have an SSL cert from submitted CSR cert request, generated from java keytool.

I currently can't upload it to AWS Load Balancer Listeners.

I'm getting the error:

"Failed to create SSL Certificate: rapidssl. Private key was in an unrecognized format."

What to put in as private key? Should I convert my .jks or .crt file to openssl pem file? How?