generate key and certificate using keytool

In your first command, you have used the -genkey option to generate the keystore named keystore.jks.

To export the certificate in .CER format file, you will need to use the -export option of the keytool.

An example is:

keytool -v -export -file mytrustCA.cer -keystore keystore.jks -alias mytrustCA

This will generate a file named mytrustCA.cer

To generate a certificate request to send to a CA for obtaining a signed certificate, you will need to use the -certreq option of keytool.

An example is:

keytool -v -certreq -keystore keystore.jks -alias mytrustCA

This will ask for the keystore password and on successful authentication, it will show the certificate request as given below (a sample).

-----BEGIN NEW CERTIFICATE REQUEST-----
MIIBtDCCAR0CAQAwdDELMAkGA1UEBhMCSU4xFDASBgNVBAgTC01haGFyYXNodHJhMQ8wDQYDVQQH
EwZNdW1iYWkxEjAQBgNVBAoTCU1pbmRzdG9ybTEUMBIGA1UECxMLRW5naW5lZXJpbmcxFDASBgNV
BAMTC1JvbWluIElyYW5pMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCqOLEumwLHlzIUAPD6
Ab1pVp84mhSNCCcUKInZbSdiDYnKSr46EjEw0PtZOVPJbM4ZG3bZsOboYr0YfViJi41o4yJICFAZ
8wCQQxPK/4N8MPV7C5WDH28kRKGH/Pc2e7CxV+as573I34QmkINk7fEyERMDwP/WgmrcKZgL0sfy
ewIDAQABoAAwDQYJKoZIhvcNAQEFBQADgYEAlcpjOUZFP9ixskXSA7HNlioWwjbL9f9rQskJ9rK8
kGLJ1td+mqqm20yo/JrKCzZjOMqr/aL6Zw2dkoyU34T9HnR2Bs3SgKn6wlYsYEVvVBk71Ec6PeTi
e+fhfNQEHsj4wuB4qixO3s1jtsLDy+DpTzYguszczwxXGFVNuk+y2VY=
-----END NEW CERTIFICATE REQUEST-----

You will need to send this Certificate REquest or paste it into the Digital Certificate signer webpage. Alternately, you can even redirect this output to a file instead of the console as follows:

keytool -v -certreq -keystore keystore.jks -alias mytrustCA > mycertreq.txt