If your work laptop had a TPM module and this was enabled, the files will only be able to opened when the USB stick is used on the work laptop, they are not accessible on other computers.
It wouldn't have mattered if you emailed them as the OS can use the TPM module send the files encrypted anyway.
Also it can leave a lot more info on the source than a normal copy does, so be very careful the files you copied belong to you.
If it is TPM encryption without the Laptop Hardware is is not possible to decrypt the files.
To understand TPM, a google search will give lots of results some of it is pretty heavy reading