I accidently put MAID into my Electrum, so I think that is the reason why my private key does not correspond to the right address. When I check my address on www.omniwallet.org it shows the right amount of MAID, but when I import my private key it shows a balance of $0.00 and gives a whole new address.

When importing my private key in www.omniwallet.org or when I enter it in www.bitaddress.org it shows a different address than my electrum.
It is about the following address (in electrum) : 3Jnz4bDfgmB9DYiZkxZX53rnYyWb3XG2pQ.
I read somewhere that an address starting with a 3 (is p2sh? and) can have multiple private keys and that it is possible that I have the wrong one. How do I retrieve the right private key corresponding to this address? Thanks in advance.