MY CURRENT VERSION IS 22-04.1 , WHEN I TRY TO INSTALL THE UPDATES FOLLOWING ERRORS ARE SHOWING .
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
Get:8 http://ci.archive.ubuntu.com/ubuntu xenial-updates InRelease [99.8 kB]
Hit:9 http://archive.ubuntu.com/ubuntu jammy-security InRelease
Err:7 http://security.ubuntu.com/ubuntu xenial-security InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
Err:8 http://ci.archive.ubuntu.com/ubuntu xenial-updates InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
Reading package lists... Done
E: The repository 'cdrom://Ubuntu 16.04.1 LTS _Xenial Xerus_ - Release amd64 (20160719) xenial Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ci.archive.ubuntu.com/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://security.ubuntu.com/ubuntu xenial-security InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ci.archive.ubuntu.com/ubuntu xenial-updates InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 40976EAF437D05B5 NO_PUBKEY 3B4FE6ACC0B21F32