QR code is just a bunch of dots on a square, it is not necessarily your private key. think of QR as barcode but instead of 1 dimension it has 2.
make sure you are using the QR code of your "private key" not QR code of your public key, or bitcoin address or anything else if you want to back up. for example in bitaddress.org the QR code on the left is your bitcoin address in base58 and the QR on the right is the private key.
p.s. private key starts with 5 or L or K
Thank you so much
QR in electrum starts with 1 so that is only public key.?
Would you know how to get private key from electrum ?
I'm worried to send BTC to some random generator :/
if it starts with 1 then it most probably is your bitcoin address like the one you see in my profile for example.
and i've read the previous comments and it seems like your wallet is old so that must be the reason you don't see the private key option when you right click on an address like this:
you can also do this:
but and as someone else already mentioned, you just need the seed. your seed is your private keys.
IF you have not imported any keys in your current wallet then all the private keys that you are seeing right now can be easily derived from that seed. that is how deterministic (or HD) wallets work.
good luck.