Import/Export wallet vi bitcoin-cli. Bitcoin abc node
importwallet is the opposite RPC of dumpwallet, not backupwallet.

backupwallet creates a copy of your wallet.dat file. You restore that file by putting it back in the data directory.

dumpwallet creates a wallet dump (just private keys, no history, addresses, labels, accounts, ...), which can be imported into an existing wallet using importwallet.