You must have an account’s keyfile to be able to send any transaction from that account. Keyfiles are found in the keystore subdirectory of your Ethereum node’s data directory. The default data directory locations are platform specific:
To backup your keyfiles (accounts), copy either the individual keyfiles within the
keystoresubdirectory or copy the entire
To restore your keyfiles (accounts), copy the keyfiles back into the
keystore subdirectory, where they were originally.