My opinion is that the best store of bitcoin is the account verified on the exchange. First, you always have the ability to quickly sell their bitcoins, and secondly you can earn by selling and buying coins. Why keep it in the fridge?
I can't believe a full member on this forum can give this kind of advice! But who am I to judge anyway? OP requested for a cold storage and you brought up an exchange as the best way? Do you even have a slight idea of what a cold storage means?
By the way, OP, if you are looking for a cold storage, I will advise you go for a hardware wallet like Trezor or Ledger Nano. They are quite affordable but if you do not have the bux, you can just go for a paper wallet instead and keep it in a very safe place.
You may also try some good light desktop wallets like electrum or exodus which gives you access to your private key. Once you open one, you can just back up your account, keep the backups safely at least offline, and only access whenever you need it. All you need is just your public address to receive bitcoins anyway. Please remember that if you are going to make use of this, desktop wallets are as safe as your PC.