Buy a Hardware wallet, using a USB flash drive to store your Bitcoin is very risky, the USB flash might stop working after some months even if you don't use at all, and they easily get corrupted too, another big headache is zero security of USB, plug into a PC and virus take the best of the USB flash.
If you don't have money for a hardware wallet, download electrum wallet online and write down the recovery phrase, the recovery phrase is your security key, keep it privately, it is meant for the user only.
Note: if someone managed to get your recovery seed they can easily import into about Bitcoin wallet and move out your funds.
Hardware wallet is more expensive than a USB drive, but if the user is very careful to treat that, 10 years and more is safe with a very high quality drive.
I have a friend who saves his bitcoin on USB drive called Tails OS (electrum wallet). It's not problem, his bitcoin is still there after 5 years. maybe not many, just under nine hundred thousand satoshis, but this shows us the USB drive is safe, just don't put in a lot of satoshis to maybe happen human error in the future
You are right Azhari, even if USB flash ended up going bad or something, the user still has the recovery seed and that's all that matters, the difference between USB flash and hardware wallet is just the security, as a hardware wallet user you still have to keep your keys very safe too, I haven't heard about this Tails OS but I have seen a friend installing some tiny Linux OS on USB Drive and keeping his wallet in the OS running Electrum Linux Appimage.