if you have all your keys, you can start locally a node. When the node is synced, submit transaction to deregister your pool. with cardano-cli by submitting a transaction with a deregistration-certificate created by the command cardano-cli stake-pool deregistration-certificate [...]
You don't have to recover the funds you pledged because you never lost control of your funds : you still have the signing key of the pledge owner address, do you ?
If you want to transfer your funds, you can create a wallet on Daedalus or Yoroi, and submit locally a payment transaction to transfer your pledged ADAs to this wallet. Be careful : sign the transactions offline.
Edited : gave more informations on the way to de-register a pool