Possible to encrypt a folder so nobody can access on Windows 10?

You can use the Encrypting File System (EFS) feature, which is used for encryption in NTFS file system. This works in Windows 10 Pro/Enterprise/Education editions.

Follow steps in this guide to encrypt the folder:

https://www.kapilarya.com/how-to-encrypt-files-and-folders-in-windows-10

Let us know if this helps!

Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.