Hi there,

I have a few flash drives branded 'kingston' and 'sandisk'.

My question, what software would you suggest to encrypt all files? Would you suggest paid or free version software?

RegardsHow much MONEY is it worth to you?
Anybody who sells you something has a legal responsibility.
WINDOWS already has built-in encryption.
Beware THOUGH...

Most Users are irresponsible with their passkeys and then come here askin how to UNLOCK...
It is always good to feel safe that your data is encrypted.

Password wouldn't be an issue.

What is it called that windows have built-in encryption?

RegardsLook here:
How to Easily Encrypt Your USB Drive in Windows 7

Don't for get the password! I have windows 10, can I use that program ?Yes, here is a link for Windows 10.
https://www.groovypost.com/howto/encrypt-flash-drive-sd-card-windows-10-bitlocker/
Quote

Flash drives and SD cards are a convenient tool for transferring data. However, with the convenience and portability, comes a security risk. That’s where encryption becomes valuable, and BitLocker in Windows 10 makes it easy to do. Plus, Windows 10 version 1151 comes with a new and improved encryption algorithm.
Note: The BitLocker encryption tool is only available in Windows 10 PRO and not the Home version.