I am actually a newbie who bought twenty (2) bitcoins in 2010 and I have only just found where I copied down the code or key. How do I get this code or key onto a wallet or USB? Please advise.
If you really purchased the Bitcoin in 2010 and wrote down a code you might have own written down an address (a string about 20-27 characters long beginning with a 1). I do not believe any of the above private key formats were available in 2010.
If you did only write down an address, what you'll want to find is a wallet.dat file.
It's also possible that you might have used a service called instawallet or mybitcoin. If so, your Bitcoins are long since gone.
If you did write down a private key, be careful to not give it to anyone else even if they offer to help. Sometimes people offer to help just to steal people's Bitcoins. Honest helpers will almost never ask for your private keys, since they don't want to be accused of stealing them if you somehow get them stolen.
You can safely describe the first digit or two, its length, and/or how many characters it has in it and that could help us determine if you'll be able to recover and what tools you'll need to use.
How do I get this code or key onto a wallet or USB?
By USB I guess you mean a hardware-wallet like the Trezor etc.
Choosing a wallet is an important step, I assume you have looked into this and are aware of the dangers of using some types of wallets and are aware of the need to never give any helpers your private-key or the password to a wallet.
There are several ways of writing down a private-key and there are mnemonic-word based systems for saving private-keys (the private-key is derived from the phrase). You should find out which sort of private-key or seed-phrase you have and make sure your chosen wallet supports it.
The general process is to first install the wallet, some wallets are full-nodes and take several days to synchronise with the Bitcoin network.
Once you have a wallet installed and ready for use, you find the menu option for importing a private key. You can then type the key into the wallet. It should then show the amount of unspent bitcoin for addresses derived from your private key.
A private-key in Wallet Import Format (WIF) might look like
A private-key in Hexadecimal format might look like
A seed phrase might look like
witch collapse practice feed shame open despair creek road again ice least. They usually have 12, 18 or 24 words chosen from a list defined in BIP39. Not all wallets used BIP39 though.
Wallets such as Electrum support this seed-phrase system which can be used for "wallet recovery".