I do not know methods to carry out this on the GUI, however with a view to import a WIF non-public key on a contemporary Bitcoin Core you must use a descriptor. As a way to get better from a backup, you almost certainly wish to use the combo() descriptor.

Right here is an instance with an instance WIF non-public key: cSWVo8YMehg6STxqw6xGgmMJE6Ac6RCJ7owcrBZRAT7QANtyAAEj (it is a testnet-encoded WIF non-public key on goal, yours will likely be completely different). There may be almost definitely the same move on the graphical interface, however failing which you can at all times use the command line (or the command enter on the GUI).

First craft a combo descriptor from this non-public key and get its checksum:

getdescriptorinfo 'combo(cSWVo8YMehg6STxqw6xGgmMJE6Ac6RCJ7owcrBZRAT7QANtyAAEj)'

We get:

{
  "descriptor": "combo(023ad6336ae257527ff59ec4356fa5d2ac33fff5e04be9e5958dfed9b0100b7948)#mv9rgx7y",
  "checksum": "9zedq5ns",
  "isrange": false,
  "issolvable": true,
  "hasprivatekeys": true
}

Now you can import this descriptor utilizing the importdescriptors command:

importdescriptors '[{"desc":"combo(cSWVo8YMehg6STxqw6xGgmMJE6Ac6RCJ7owcrBZRAT7QANtyAAEj)#9zedq5ns","timestamp":"now"}]'

Lastly rescan the blockchain from a degree earlier than which you’re sure to not have acquired cash. To rescan the entire chain from the genesis block don’t present any parameter:

rescanblockchain