If you have a wallet recovery mnemonic, then you were likely using MultiBit HD... as multibit classic did not use recovery mnemonics.
Which is a bit confusing, as you say you have a single address with QR Codes for the address and private key... as that is a paper wallet, and from memory was not a feature in MultiBit HD. So, I'm thinking that maybe the "recovery mnemonic" and the "paper wallet" are not actually related.
To recover using the wallet recovery mnemonic, you can enter that into another BIP39 compatible wallet. I would recommend that you use Electrum:
https://www.electrum.org/#downloadONLY download from the official site as linked... and follow this excellent tutorial on how to verify that download before using it:
https://bitcointalk.org/index.php?topic=5240594.msg54223763#msg54223763Once you have Electrum setup:
- create a new wallet
- select "standard wallet"
- select "I already have a seed"
- click the "Options" button and tick the "BIP39 seed" box
- Enter your recovery mnemonic (it should say next to the options button "BIP39 (checksum: OK)".
- On the next page, Electrum should prompt you for the address type... click the "Detect existing accounts" button
At this point, Electrum will hopefully find your old addresses/transactions/private keys etc... If it does not, the appropriate settings are:
- Select "Legacy (p2pkh)"
- Change the derivation path to: m/0'
That will restore your multiBit HD wallet into Electrum.
As for the piece of paper with the QR codes, you can also import that into Electrum, but instead of using the "standard wallet" option... use the "Import bitcoin addresses or private keys" option when creating the wallet and then scan the "redeem" barcode. (or enter the private key manually... it should start with a "5" and "L" or a "K")
If you don't have a webcam, you can trying using a mobile wallet (like Mycelium or Electrum - Android) to scan the "redeem" QR code.